Biologically Active Substances From Amino Acid: An Overview

Most amino acids are obtained from the degradation of dietary and turnover of body protein. consumption of excess proteins leads to increased degradation as they are generally not stored and their nitrogen and 

carbon skeleton are processed separately. the carbon skeleton of amino acids can have the following fates:

About !0% to 15% of body energy requirement are fulfilled from complete oxidation by TCA cycle (tricarboxylic acid cycle ). this can vary depending on the amount of dietary protein consumed.

 

Gluconeogenesis

Synthesis of lipid , fatty acid and ketone bodies.

Synthesis  of non essential amino acids.

In the section we will discuss the role of amino acid as biosynthetic precursors. the detailed pathways for some of them shall be described in subsequent units.

Some amino acids serve as precursors for the synthesis of nitrogen containing compound such as nucleotides porphyrins nitric oxide ,etc beside that decarboxylation of amino acid produces monoamines, also known as biogenic amines.

Some nitrogen compounds derived from amino acids

Nitrogen containing compound             Amino acid precursor(s)

purine                                                          glutamine ,aspartate and glycine

pyrimidine                                                   glutamine and aspartate

porphyrins                                                   glutamine and aspartate

creatine                                                        glycine, arginine and methionine

taurine                                                         cystine/ cysteine

melanin                                                        tyrosine

nitric oxide (No)                                          Arginine

Biogenic amines derived from amino acids

Biogenic Amines                                       Amino acid

Catecholamines                                           Tyrosine

Serotonin and melatonin                             Tryptophan 

Histamine                                                    Histidine

Y-amino butyrate(GABA)                           Glutamate 

Polyamines                                                 Ornithine &methionine

Denovo Synthesis Of Nucleotide

You are aware of the structure of nucleotide -the building blocks of RNA and DNA. all nucleotide have  nitrogenous bases (purines and pyrimidines ) as one of their constituent .a purine is a heterocyclic aromatic organic compound that consists of a pyrimidine ring fused to an imidazole ring. the amino donors of a purine ring are glutamines and aspartate whereas glycine is completely incorporated the two purine nucleotide are formed by a branched pathway.

The origin of n and c of a heterocyclic purine ring

The amino acids ,aspartate and glutamine are required for the de novo pyrimidine biosynthesis . the amide nitrogen of glutamine is the amino donor and aspartate is completely incorporated into the pyrimidine ring .the two pyrimidine ribonucleotides are synthesised from a common linear pathway.

porphyrine

porphyrins are hetrocyclic organic compound in which the adjacent pyrrole subunits are interconnected via methenyl bridge (=CH) . A pyrrole is five member ring compound with four carbon and a nitrogen atom .all porphyrins are derivatives of a parents tetrapyrrole ,porphin .porphyrins have the ability to make coordination bonds with metal ions. an important example of porphyrins is heme pigment bound to globin protein present in red blood cells .

The synthesis of porphyrins is initiated with the formation of a -amino levulinic acid (a -ALA) which  is formed either from condensation of condensation of succinyl coA and glycine or directly from glutamate.

Creation and creatine phosphate 

creatine  phosphate is an important reservoir of high energy phosphate group in skeletal muscle ,brain and heart .it can readily  transfer  its phosphate group to ATP. the amino acids arginine ,glycine and S-adenosyl methionine  (SAM) are  needed for creatine synthesis. the enzyme are distributed partly in kidney and liver. the tissues dependent on creatine  phosphate replenish their creatine pools from plasma.