Chemistry- Enzymes

d Obstructive jaundice is characterized by an increased ALP- 3x the ULN- and a marked increase in GGT. The aminotransferases are slightly elevated owing to the fact that they are sensitive for acute hepatocellular conditions.

Given the following results: ALP marked increase AST slight increase ALT slight increase GGT marked increase This is most consistent with: a. acute hepatitis b. osteitis fibrosa c. chronic hepatitis d. obstructive jaundice

c Increased levels of aldolase and CK are seen with skeletal muscle disease. The magnitude of the elevation is dependent on the type of skeletal muscle disease.

A 10 year old child was admitted to pediatric with an initial diagnosis of skeletal muscle disease. The best confirmatory tests would be: a. creatine kinase and isocitrate dehydrogenase b. gamma-glutamyl transferase and alkaline phosphatase c. aldolase and creatinine kinase d. lactate dehydrogenase and malate dehydrogenase

a Erythrocytes contain 150x more LD activity than serum, mostly LD1 and LD2. Rupture of the RBC membranes as in hemolysis will elevate the serum level of the enzyme. LD5 is increased in liver disorders and drug toxicity if the liver is involved.

A common cause of a falsely increased LD1 fraction of lactic dehydrogenase is: a. specimen hemolysis b. liver disease c. congestive heart failure d. drug toxicity

d Amylase is present primarily in the pancreas. Pancreatitis results in the release of the enzyme into the serum. Creatinine is a nonprotein nitrogenous substance and is measured for renal function. Beta-hydroxybutyrate is measured for diabetic acidosis and LD isoenzymes are evaluated for disorders involving the heart and liver

A physician suspects his patient has pancreatitis. Which test (s) would be most indicative of this disease? a. creatinine b. LD isoenzyme c. beta-hydroxybutyrate d. amylase

c Although, CKMB activity is more specific for the myocardium, CKMM is present in both the skeletal and heart muscles. An increase of the isoenzyme activity may occure after a AMI. Only one peak would be present for a brain tumor and muscular dystrophy; no peaks would be present for hepatitis since the liver is not a tissue source of CK.

A scanning of a CK isoenzyme fractionation revealed 2 peaks: a slow cathodic peak (CKMM) and an intermediate peak (CKMB). A possible interpretation for this pattern is: a. brain tumor b. muscular dystrophy c. myocardial infarction d. viral hepatitis

a Elevation of the leels of CK and AST is seen in muscle damage due to the crush injury to the thigh. AST levels can increase up to 4-8x the ULN. Cerebrovascular accident and pulmonary infarction have increased CKBB levels. In acute hepatitis, the AST level may be 100x the ULN.

A serum sample drawn in the ER from a 42 yr old man yielded the following: Patient Reference range CK 185 U/L 15-160 U/L AST 123 U/L 0-48 U/L CKMB 6 U/L 2-12 U/L Which of the following conditions might account for these values? a. crush injury to the thigh b. cerebrovascular accident c. pulmonary infarction d. early acute hepatitis

b AST belongs to the class of transferase enzymes. Specifically, AST catalyzes the transfer of an amino group from aspartate to alph-ketoglutarate forming oxaloacetate and glutamate.

Amino transferase enzymes catalyze the: a. exchange of amino groups and sulfhydryl groups between alpha-amino and sulfur-containing acids b. exchange of amino and keto groups between alpha-amino and alpha-keto acids c. hydrolysis of amino acids and keto acids d. reversible transfer of hydrogen from amino acids to coenzyme

a The major LDH isoenzymes in the serum of healthy persons are LD2, accounting for 29-39% of the total activity and LD1=14-26% of enzyme activity. In a myocardial infarction the pattern is changed. The activity of LD1 is greater than LD2. The ratio of LD1 to LD2 is >1. The normal ratio is 0.45-0.74.

An electrophoretic separation of lactate dehydrogenase isoenzymes that demonstrates an elevation in LD-1 and LD-2 in a "flipped" pattern is consistent with: a. myocardial infarction b. viral hepatitis c. pancreatitis d. renal failure

a Aspartate aminotransferase (AST) is involved in the transfer of an amino group between aspartate and alpha-keto acids. AST is present in several tissues, with its highest concentrations in cardiac tissue, liver and skeletal muscle. Depending on the type of liver disease, the levels may be 100x the upper limits of normal (ULN)

Aspartate amino transferase (AST) is characteristically elevated in diseases of the: a. liver b. kidney c. intestine d. pancreas

b The transferases, ALT and AST are located primarily in the liver. Elevated serum levels of the enzymes are seen in hepatocellular disorders. The levels may be 100 times the ULN. The ALT level is usually higher than AST. Increased levels of AST are also seen in infectious mononucleosis and muscular dystrophy, but ALT is not elevated in the clinical disorders.

Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are both elevated in which of the following diseases? a. muscular dystrophy b. viral hepatitis c. pulmonary emboli d. infectious mononucleosis

a In acute hepatocellular disorders, the serum levels of AST and ALT can be 100x the ULN. Slight increases of the enzyme activities are seen in chronic hepatitis, hemangioma, and obstructive jaundice.

Given the following results: ALP slight increase AST marked increase ALT marked increase GGT slight increase This is most consistent with: a. acute hepatitis b. chronic hepatitis c. obstructive jaundice d. liver hemangioma

b Chronic hepatitis is a chronic inflammation of the hepatocytes that persists for at least 6 months. The serum enzyme levels may be variable depending on the condition. ALT, AST, and ALP may be increased by 2x the ULN. GGT is slightly increased.

Given the following results: ALP slight increase AST slight increase ALT slight increase GGT slight increase This is most consistent with: a. acute hepatitis b. chronic hepatitis c. obstructive jaundice d. liver hemangioma

a In the immunoinhibition technique for CKMB determination, antibodies are directed against the M and B units of the enzymes. Anti-M inhibits all M activity but not B activity. CK activity is measured before and after inhibition. The activity remaining after inhibition is a result of the B subunit for BB and MB activity.

In the immunoinhibition phase of the CKMB procedure: a. M subunit is inactivated b. B subunit is inactivated c. MB is inactivated d. BB is inactivated

b Creatine kinase (CK) is located in brain tissue and heart and skeletal muscle. Diseases involving the tissue site will increase the level of the enzyme activity. CK activity is not increased in hepatitis

In which of the following conditions would a normal level of creatine kinase be found? a. acute myocardial infarct b. hepatitis c. progressive muscular dystrophy d. intramuscular injection

b The LD1 and LD2 fractions are increased in hemolytic anemia due to the intramedullary hemolysis. LD5 is increased with hepatic damage. LD3 may be increased with acute pancreatitis. The LD isoenzyme pattern in renal disease is very similar to a normal pattern except for the higher absolute values.

Increased serum lactic dehydrogenase activity due to elevation of fast fraction (1 and 2) on electrophoretic separation is caused by: a. nephrotic syndrome b. hemolytic anemia c. pancreatitis d. hepatic damage

d LD4 and LD5 isoenzymes are located iin the liver and skeletal muscle. LD5 is the predominant fraction in these tissues. Elevated levels of LD5 are seen with intrahepatic disorders. LD1 and LD2 are elevated in hemolytic anemia and myocardial infarction. LD3 fraction is increased with pulmonary infarction.

Increased total serum lactic dehydrogenase (LD) activity, confined to fractions 4 and 5 is most likely to be associated with: a. pulmonary infarction b. hemolytic anemia c. myocardial infarction d. acute viral hepatitis

d Isoenzymes are multiple forms of an enzyme that possess the ability to catalyze a reaction, but differ in structure. For enzymes located in many tissue sites, an increased total enzyme activity cannot be associated with a specific clinical disorder. However, since the isoenzyme fractions are located in various tissue sources, measurement of the different fractions are considered a more specific indicator of various disorders than total levels

Isoenzyme assays are performed to improve: a. precision b. accuracy c. sensitivity d. specificity

c All of the enzymes are dehydrogenases which are oxidoreductases. The oxidoreductases catalyze oxidation reduction reaction between 2 substrates. The enzymes may be located in the liver and the heart; however, the enzymes are in class 1 and not class 3 according to the enzyme commission of the IUB system.

Lactate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase, and hydroxybutyrate dehydrogenase all: a. are liver enzymes b. are cardiac enzymes c. catalyze oxidation-reduction reactions d. are class III enzymes

d In the coupled reaction of AST measurement, malate dehydrogenase catalyzes the oxidation of oxaloacetate to malate in the indicator reaction

Malic dehydrogenase is added to the aspartate aminotransaminase (AST) reaction to catalyze the conversion of: a. alpha-ketoglutarate to aspartate b. alpha-ketoglutarate to malate c. aspartate to oxalacetate d. oxalacetate to malate

a Elevations of serum LD4 and LD5 fractions are seen in liver and skeletal muscle diseases becasue the isoenzymes are located in the tissues. LD1 and LD2 are elevated in hemolytic anemia and myocardial infarction. Increased levels of LD3 are observed in pulmonary edema.

Of the following diseases, the one most often associated with elevations of lactate dehydrogenase isoenzymes 4 and 5 on electrophoresis is: a. liver disease b. hemolytic anemia c. myocardial infarction d. pulmonary edema

d The LD isoenzymes as a percentage of total LD activity are LD1: 14-26%, LD2: 29-39%, LD3: 20-26%, LD4: 8-16% and LD5: 6-16%. The scan indicates the fraction LD5 is increased. Elevated levels of LD5 are seen with viral hepatitis.

P.115 #180

d The Regan isoenzyme is an abnormal ALP isoenzyme. The carcinoplacental ALP has properties similar to the placental enzyme, in that it is also heat stable (65C, 30 min). It has been detected in lung, breast, ovarian and colon cancer.

Regan isoenzyme has the same properties as alkaline phosphatase that originates in the: a. skeleton b. kidney c. intestine d. placenta

d Lactate dehydrogenase (LD) catalyzes the interconversion of lactic and pyruvic acids. Electrophoretically, using agarose or cellulose acetate medium, LD can be separated into 5 isoenzymes, LD1-LD5. CK and lipase have 3 isoenzymes; AST has 2.

The enzyme present in almost all tissues that may be separated by electrophoresis into 5 components is: a. lipase b. transaminase c. creatine kinase d. lactate dehydrogenase

d Creatine kinase (CK) catalyzes the reversible phosphorylation of creatine. The highest levels of the enzyme are found in skeletal muscle, heart muscle and brain tissue. Increased serum enzyme activity is present in diseases involving the listed muscles and tissue. Lipase is measured for acute pancreatitis; the transaminase and lactate dehydrogenase (LD) are not markedly increased in muscular dystrophy.

The enzyme, which exists chiefly in skeletal muscle, heart, and brain, is grossly elevated in active muscular dystrophy, and rises early in myocardial infarction is: a. lipase b. transaminase c. lactate dehydrogenase d. creatinine kinase

a AST and ALT levels are the highest in acute hepatocellular conditions, specifically acute viral hepatitis. The levels may be 100x the ULN. Slight increases of the aminotransferases are seen in cirrhosis and metastatic hepatic carcinoma

The greatest activities of serum AST and ALT are seen in which of the following? a. acute viral hepatitis b. primary biliary cirrhosis c. metastatic hepatic cirrhosis d. alcoholic cirrhosis

b The major serum ALP isoenzymes are located in the liver, bone, intestine, and placenta. Placenta ALP is most heat stable followed by the intestinal, liver and bone fractions in decreasing order of stability.

The most heat labile fraction of ALP is obtained from: a. liver b. bone c. intestine d. placenta

c GGT levels are elevated in alcoholism. The levels may range from 2-3x the ULN. ALT, AST, and ALP may be increased depending on the alcohol damage to the liver.

The most sensitive enzymatic indicator for liver damage from ethanol intake is: a. ALT b. AST c. GGT d. ALP

d There is an increase in the serum levels of amylase and lipase in acute pancreatitis. However, the elevated level of lipase persists longer than amylase. Elevated levels of lipase and amylase are seen in other intra-abdominal conditions, but the frequency of elevations is less with lipase than amylase.

The most specific enzyme test for acute pancreatitis is: a. acid phosphatase b. trypsin c. amylase d. lipase

c Of the 3 CK isoenzymes, CKMB is located in the myocardial. The fraction is elevated with an acute myocardial infarction. (AMI). CKMM is elevated in acute muscular stress following strenuous exercise. CKBB is increased brain injury.

The presence of increased CKMB activity on a CK electrophoresis pattern is most likely found in a patient suffering from: a. acute muscular stress following strenuous exercise b. malignant liver disease c. myocardial infarction d. severe head injury

b The 3 CK isoenzymes are CK1 or CKBB, CK2 or CKMB, CK3 or CKMM. CKMB is primarily located in myocardial tissue. Damage to the myocardial will cause an elevation of the CKMB level.

The presence of which of the following isoenzymes indicates acute myocardial damage? a. CK-MM b. CK-MB c. CK-BB d. none

a The holoenzyme is the active system formed by a protein portion called the apoenzyme and a cofactor which can be an activator if inorganic and a coenzyme if organic

The protein portion of an enzyme complex is called the: a. apoenzyme b. coenzyme c. holoenzyme d. proenzyme

b The heat activation method of ALP isoenzyme separation involves heating an aliquot of serum sample at 56C for 10 minutes. An untreated aliquot of the sample along with the heated one are assayed for ALP activity.

What specimen preparation is commonly used to perform the ALP isoenzyme determination? a. serum is divided into 2 aliquots, one is frozen and the other is refrigerated b. serum is divided into 2 aliquots, one is heated at 56C and the other is unheated c. no preparation is necessary since the assay used EDTA plasma d. protein-free filtrate is prepared first

a After an acute myocardial infarction (AMI), CK activity increases 4-6 hours after the symptoms, peaks at 12-24 hours and returns to normal within 48-72 hours. AST increases 6-8 hours after the infarction. Elevated levels of LD are noted 12-24 hours after the symptoms. ALT activity does not increase with a AMI.

When myocardial infarction occurs, the first enzymes to become elevated is: a. CK b. LD c. AST d. ALT

c Approximately 20%-30% of seminal fluid is prostatic fluid. The composition of the prostatic fluid is acid phosphatase, citric acid, and proteolytic enzymes. The activity of prostatic acid phosphatase may be measured in seminal fluid for medicolegal cases involving rape.

Which of the following chemical determinations may be of help in establishing the presence of seminal fluid? a. lactic dehydrogenase (LD) b. isocitrate dehydrogenase (ICD) c. acid phosphatase d. ALP

d Elevated serum levels of LD up to 50 times the ULN are seen with pernicious anemia. The ineffective eryhtropoiesis results in the release of large quantities of LD1 and LD2. Increased levels of LD1 and LD2 may be seen in renal disease, but the increase is not as great as for pernicious anemia. Slight increases of LD3 are seen in pulmonary conditions and pancreatitis

Which of the following clinical disorders is associated with the greatest elevation of lactate dehydrogenase isoenzyme 1? a. pneumonia b. glomerulonephritis c. pancreatitis d. pernicious anemia

c Thymolphthalein monophosphate is the substrate of choice for quantitative endpoint reactions; however, p-nitrophenylphosphate is the preferred substrate for continuous monitoring.

Which of the following enzyme substrates for prostatic acid phosphatases is best for the continuous monitoring method? a. phenyl-phosphate b. thymolphthalein monophosphate c. alpha-naphthyl-phosphate d. beta-glycerophosphate

a Amylase and lipase are hydrolases involved in the breakdown of starch and glycogen, and lipid metabolism, respectively. Both enzymes are primarily located in the pancreas. Disorder of the pancreas are characterized by elevated levels of the enzymes. 5'NT, GGT, AST, and LD are elevated in liver and hepatobiliary diseases.

Which of the following enzymes are used in the diagnosis of acute pancreatitis? a. amylase (AMS) and lipase (LPS) b. aspartate aminotransferase (AST) and alanine aminotransferase (ALT) c. 5'-nucleotidase (5'N) and gamma-glutamyl transferase (GGT) d. aspartate aminotransferase (AST) and lactate dehydrogenase (LD)

b In the amyloclastic, saccharogenic and chromogenic methods for measurement of amylase, the substrate, starch is converted to glucose and maltose.

Which of the following enzymes catalyzes the conversion of starch to glucose and maltose? a. malate dehydrogenase (MD) b. amylase (AMS) c. creatine kinase (CK) d. isocitric dehydrogenase (ICD)

b Macroamylasemia is an asymptomatic condition which results when the amylase molecule and immunoglobulins combine to form a complex. The complex is too large to be filtered across the glomerulus. Lack of renal clearance leads to an increased serum amylase and a decreased urine amylase

Which of the following sets of results would be consistent with macroamylasemia? a. normal serum amylase and elevated urine amylase values b. increased serum amylase and normal urine amylase values c. increased serum and urine amylase values d. normal serum and urine amylase values