Amino acids semi-essential

Other milestones in research on the biological significance ofNO in vascular homeostasis were the description of the molecular pathway of NO biosynthesis by NO synthase fixrm a semi-essential amino acid, L-arginine (Palmer et al, 1988), and the identification of this enzyme and its role as modulator of platelet function in human platelets (Radomski et al, 1990a). 

Amino acids essential semi-essen- non-essen- BCAA AAA polar ketogenic glucogenic... 

Most of the prokaryotic and many eukaryotic organisms (plants) are capable of synthesizing all the amino acids present in the protein. But higher animals including man possess this ability only for certain amino acids. The other amino acids, which are needed for normal functioning of the body but cannot be synthesized from metabolic intermediates, are called essential amino acids. These must be obtained from the diet and a deficiency in any one of the amino acids prevents growth and may even cause death. Methionine, Threonine, Tryptophan, Valine, Isoleucine, Leucine, Phenylalanine and Lysine are the essential amino acids, however, Histidine and Arginine are considered semi essential amino acids as it can be partly synthesized by the body. 

Arg is a glucogenic amino acid, and it is semi-essential for humans, rats and chicks, i.e. it is not required by the adults of these species, but the young animals are unable to synthesize it rapidly enough to satisfy their total needs for growth and development. Arg is synthesized in the Urea cycle (see) where it serves as an important intermediate. It is attacked by various enzymes, depending on the species 1. arginase (EC 3.5.3.1) hydrolyses Arg that is released pro-... 

Cystine is a semi-essential amino acid in the newborn or premature infant owing to the inactivity of cystathionine synthase and cystathionase, which are needed to convert methionine to cystine. Cows milk protein and especially casein are low in cystine and rich in methionine diluted cows milk and casein based formula cause... 

The amino acids are termed as a-amino acids if both the amino and carboxylic groups are attached to same carbon atom. The a-carbon atom is linked to side chain which is different for all the 20 amino acids found in proteins. Table 3 provides a list of all the 20 amino acids. Amino acids are also referred to as residues in molecular biophysics. Of the amino acids. Arginine, Valine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Tryptophan and Threonine are Essential Amino Acids as they can t be synthesised by the human body. However, Histidine and Arginine can be synthesised in the adult body even if not in growing children, and can therefore also be known as Semi-Essential Amino Acids. The rest all are Non-Essential or Dispensable Amino Acids as they can be formed by the body. Molecular structure of the amino acids is shown in Figs. 13, 14, 15, and 16. 

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