The absorption of amino acids

Amino acids can be actively and passively absorbed. Active absorption of amino acids includes:

1) absorption with participation of ATP-ases (due to creature of gradient of concentration of Sodium ions);

2) absorption with participation of gamma-glutamyl-transpeptidase (GGT):

glutathioneàglycylcysteyl+gamma-glutamyl (this reaction occurs in cytosol of intestinal cell. Then gamma-glutamyl exits from intestinal cell on its surface and there interacts with amino acid, forming dipeptide “gamma-glutamyl-transported amino acid”

gamma-glutamyl+amino acidàgamma-glutamyl-amino acid (this reaction occurs under action of GGT). Formed dipeptide sinks into cytosol of intestinal cell and there is hydrolyzed to gamma-glutamyl and amino acid which is used in intestinal cell or exits in portal vein. Gamma-glytamyl joins with glycylcysteyl yielding glutathione again.

The intermediate Metabolism of Simple Proteins (part 1): the conversion of amino acids in tissues. The formation and usage of Creatine. The decarboxylation of amino acids, the role of biogenic amines

The usage of amino acids in tissues:

90% of amino acids are used for anabolic processes: 1) 80% for biosynthesis of proteins including Hormones and enzymes; 2) 10% for a) biosynthesis of biologically active peptides, for example neuropeptides; b) biosynthesis of non-protein’s substances, for example Creatine, Coenzymes, amino acids, Purines, Pyrimidines, Choline, coupled bile acids etc; c) reactions of detoxification, for example Glycine is used for detoxification of benzoic acid (it results in formation of Hyppuric acid); Glutamic and Aspartic acids are used for detoxification of Ammonia (it results in formation of Gln and Asn).

10% of amino acids undergo the catabolic processes (deamination and decarboxylation).

The formation and usage of Creatine:

1-st stage occurrs in kidneys: glycine+arginineàornithine+guanidinoacetic acid

2-nd stage: guanidinoacetic acid + methionineàcreatine + homocysteine

Creatine is used in muscles and heart: Creatine+ATP↔ Creatinephosphate+ADP (enzyme – Creatinekinase)

The formation of Hyppuric acid:

Benzoic acid + glycineàhyppuric acid (this reaction occurs in liver)

Catabolic processes are deamination and decarboxylation.

Decarboxylation of amino acids results in formation of biogenic (proteinogenic) amines

1) histidine à histamine+ CO2

The role of Histamine: 1 – dilatation of vessels; 2 – mediator of inflammation and allergy; 3 – stimulation of HCl secretion

2) 5-hydroxytryptophanàserotonin+CO2

The role of Serotonin: 1 – constriction of vessels; 2 – mediator of nervous system; 3 – stimulation of peristalsis of intestine

3) glutamic acidà gamma-glutamyl + CO2

The role of GABA: 1 – improves blood supplying of brain; 2 – brake mediator of nervous system. Therefore it is used in medicine as anticonvulsive drug; 3 – cyclic derivative of GABA (“Pyracetam” is used for improvement of mental functions

4) aspartic acidà beta-alanine+CO2

Beta-alanine is a constituent of HSCoA