Amino Acid Metabolism

What is the primary route to synthesize non-essential amino acids?

Synthesized from common intermediates that are part of the TCA cycle (pyruvate, oxaloacetate, and alpha-ketoglutarate) transamination

What are neurotransmitters synthesized from?

nitrogen derived from amino acids

How is catabolism broadly classified?

1. Glucogenic - amino acids whose catabolism yields pyruvate or one of the intermediates of the TCA cycle 2. Ketogenic - amino acids whose catabolism yields either acetoacetate or acetyl-CoA or acetoacetyl-CoA

Discuss the tissue inter-relationships in the fasting state.

- Blood glucose levels drop. - Insulin decreases and glucagon increases. - Glycogenolysis in liver is induced. The brain and RBCs use the glucose released by the liver. - Adipose releases FFAs and glycerol from stored TGs. The muscle and liver use FAs for energy. - The liver converts FA-derived Ac-CoA to ketone bodies that are used as energy by the brain and muscles. - Protein in the muscle is broken down and amino acids travel to the liver to be used as gluconeogenesis precursors. - Amino acid metabolism in liver generates urea that travels to the kidneys for excretion. - Lactate produced in the RBCs and glycerol made in the adipose return to the liver for gluconeogenesis.

Discuss the tissue inter-relationships in fed state.

- Blood glucose levels increase - Insulin increases and glucagon decreases. - Glucose is stored as glycogen. - Glucose is also stored as triglycerides (TG) - Amino acids also go to the liver and is converted to acetyl CoA and energy is also stored into TG. - Glucose is used in the brain and RBC. - Glucsoe is also stored as glycogen in muscle. - TG is stored in adipose tissue. - Insulin stimulates amino acid uptake and protein synthesis.

How are non-essential amino acids synthesized?

All amino acids (except for tyrosine) are synthesized from common intermediates that are part of the TCA cycle. -pyruvate -oxaloacetate - alpha-ketoglutarate

What is the final breakdown product of amino acids?

Ammonia, which is converted to urea and is rapidly removed from the body.

Why do we need inter-organ amino acid exchange?

Factors effecting amino acid exchange: 1. when the body needs energy supply then amino acids need to be exchanged between organs. 2. Many of the disease conditions increase the demand for amino acids (stress, injury, sepsis, infeciton, etc.)

Define glucogenic and ketogenic amino acids.

Glucogenic amino acids are those that produce pyruvate or one of the intermediates from the TCA cycle from their catabolism. Ketogenic amino acids are those that produce acetoacetate or acetyl-CoA from their catabolism.

What is tyrosine synthesized from?

L-Phenylalanine

How is L-tyrosine synthesized?

L-phenylalanine

What is the difference between nonessential amino acids and essential?

Nonessential - amino acids that can be synthesized in sufficient amounts from the intermediates of metabolism or from essential amino acids. Essential - amino acids that must be obtained from the diet and cannot be synthesized by the body

Explain transamination and deamination reactions.

Transamination is the transfer of an amino group to a ketoacid to make a new amino acid. catalyzed by aminotransferase Deamination is the removal of an amine group from an amino acid. Catalyzed by deaminases.

What is transamination and deamination?

Transamination: transfers an amino group to a ketoacid to form new amino acids. Catalyzed by aminotransferases. Deamination: removal of an amine group from an amino acid. Catalyzed by deaminases.

Describe inter-organ amino acid exchange.

When the body needs energy and supplies are low, amino acids must transfer between organs to supply Many disease conditions increase the demand for amino acids. Skeletal muscles are major site of protein synthesis and degradation. In fasting, metabolic acidosis, septic stress and trauma degradation of muscle protein is stimulated by cortisol. Skeletal muscle is a major site of gluatmine synthesis from branched chain amino acids. Glucagon increases skeletal muscle protein degradation.

What is the final product of amino acid metabolism?

ammonia

What is the brain a net producer of?

glutamine