Which is a niacin sparing amino acid:

Ans. (a) TryptophanRef.: Harper's Biochemistry 30th edtt. I3l6y 547, 5517;Food-facts and principles by N. Shakuntala, P 71* Niacin can be synthesized by the bacteria of the intestinal flora and is formed in the tissues from amino acid tryptophan, which has niacin sparing activity. This explains why some food rich in tryptophan e.g. milk and egg, have a far greater niacin potency than would be expected from their actual content of niacin.* In humans, deficiency of niacin results in weakness and indigestion followed by ulcerated mouth and tongue.TRYPTOPHAN* It is an essential amino acid, which is a precursor of melatonin, 5-HLAA and serotonin60 mg of tryptophanVit B6-----1 mg of Niacin.* In deficiency of vitamin B6, the pathyway altered and leads to formation of xanthuric acid. Thus XANTHURIC ACID IS THE INDEX OF VITAMIN B6 DEFICIENCY.AMINO ACID AT A GLANCE: total AA = 20 in numberESSENTIAL AA: can't be synthesized. (Mn: TV TILL 8 PM)Semi-essential AA: can be synthesized under normal condition as per demand.Non-EssentialAA: synthesized in body readilyThreonine, Valine,Tryptophan,Isoleucine, Lysine,Phenyalanine,MethionineLeucineHistidineArginineThe remaining 10 AA are Non- essential.* Sulphur containing amino acid: CYSTEINE AND METHIONINE* BASIC AMINO ACID:# HISTIDINE# LYSINE# ARGININE (most basic amino acid)* Most stable amino acid at physiologic pH: HISTIDINE* TYROSINE: non-essential AA, which is converted to Melanin, T3, T4 hormone by enzyme Tyrosinase.# Deficiency of Tyrosinase - Albinism# Deficiency of melanocyte - Vitiligo