Question

List the all seven processes involved in the steady-state active protein concentrations in a cell. Give a specific example of how the cell controls four of these processes.

Answer 1

A steady-state active protein concentration in a cell is maintained by a variety of anabolic and catabolic activities on protein components, aminoacids. These processes include

1. Transamination

2. Transdeamination

3. Oxidative deamination

4. Non-oxidative deamination

5. Removal of nitrogenous end products

6. Gluconeogenesis

7. Transamidation

Transamination transfers the amino group of an amino acid (alanine) to a keo acid (alpha ketoglutarate). This changes the latter to a new amino acid and the original amino acid into a new keto acid (pyruvate).

2. Transamination redistibutes amino-N among amino acids, removes amino groups from amino acids, produces gluconeogenic products.

Transdeamination is transamination followed by oxidative deamination. one example is alanine or glutamate transfers aminoacid to glyoxylate which is converted to glycine which in turn is converted to imino acid by glycine oxidase.

3. Oxidative deamination by amino acid oxidases (as seen in above picture). Amino acid is oxidized to imino acid which reacts spontaneously with water to produce alpha keto acid and ammonia.

4. Non-oxidative deamination is less important process, done by amino acid lyases, for example, they deaminate significant amounts of histidine and aspartic acid.

5. removal of nitrogenous products, in humans, is by removing urea from the body by excretion. Urea is formed by ornithine cycle.

6. gluconeogenesis is the formation of glucose from amino acids. Many amino acids are gluconeogenic. Thus the concentration of them can be regulated.

7. Transamidation is the process helping in ammonia detoxication, thus keeping nitrogen concentration of protein in normal level.