Introduction to ACIDIC AMINO ACIDS (Aspartate and Glutamate)
ASPARTATE AND ASPARAGINE (Acidic Amino Acids)
- Aspartate and asparagine are interconvertible
- L-asparaginase is used as an anticancer agent in the treatment of leukemias and lymphomas
Salient features of aspartate metabolism are given below
- Asp contributes one amino group for the synthesis of urea
- Malate- Aspartate shuttle transfers the reducing equivalents from the cytosol to the mitochondria
- Aspartate contributes the synthesis of purines and pyrimidines
- Aspartate along with glutamate depolarise neurons. Asp acts as a excitatory neurotransmitter in pyramidal cells and spiny stellate cells in the visual cortex.
GLUTAMATE AND GLUTAMINE
- Glutamine is synthesized from glutamate by glutamine synthetase and is converted to glutamate by glutaminase
- Most AA transfer their amino group to – ketoglutarate to form glutamate (transamination)
- Glutamate is also formed during the metabolism of histidine, arginine and proline
- Gluatamate is glucogenic and non essential amino acid.
Synthesis of biologically important substances from glutamate
- N- acetylglutamate
- γ- carboxyglutamate
- Glutamate as a neurotransmitter
- γ-Aminobutyric acid
BASIC AMINO ACIDS (Lysine, Arginine, Histidine and Proline)
- Ketogenic amino acid
- Absent in the proteins of cereals.
- Upon hydroxylation forms hydroxylysine
- Lysine in histone proteins occur in the methylated form
- Trimethyllysine serves as a precursor for the synthesis of carnitine.
- The vasodilator
- Formed from histidine by decarboxylation
- Causes a lowering of blood pressure
- Stimulates gastric secretions
- In high concentration it causes allergic reactions
- Semi-essential amino acid
- Formed in the urea cycle
- Arginine is catabolised to form glutamate which is transaminated to α-KG.
- Glycogenic amino acid
- Arginine along with glycine and SAM takes part in the creatine formation
- Arginine acts as the precursor of nitric oxide (NO)
- Glycogenic amino acid
- Proline is hydoxylated by the enzyme prolyl hydroxylase to hydroxyproline.
- Important constituent of fibrous proteins –collagen, elastin and keratin
- Increased levels of hydroxyproline excreted in urine is a diagnostic indicator of bone tumours.
- It is a potent vasodilator. Plays important role in regulation of normal BP
- Deficiency of NO may lead to hypertension
- It acts as as inhibitor of platelet aggregation and adhesion
- Acts as a neurotransmitter
- It stimulates the release of hormones (GHRH, CRH) from the hypothalamus
- It is involved with the potential bactericidal actions of macrophages including their ability to kill cancer cells
- It causes smooth muscle relaxation resulting in reduced GI motility and relaxation of sphinctors.
- Sildenafil (viagra) drug inhibits the degradation of cGMP by phosphodiesterase and is a popular drug in treating erectile dysfunction.
Therapeutic effects of NO
- NO as nitroglycerine is used in the treatment of angina pectoris
- Inhalation of NO gas is employed in the treatment of pulmonary hypertension
AROMATIC AMINO ACIDS
Phenylalanine, Tyrosine and Tryptophan
Conversion of Phenylalanine to tyrosine
Biologically Important Substances synthesized from phenylalanine and tyrosine
- Synthesis of catecholamines
- Synthesis of Thyroid hormones
- Synthesis of melanin
Other Biochemistry Notes
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