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Biochemistry

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Vitamins, Harmones and Hemoglobin

Question
14 out of 82
 

People eating only maize as staple diet develop niacin deficiency due to



A low niacin
B low tryptophan

C high leucine
D high isoleucine

Ans. C High Leucine

Niacin Deficiency (Pellagra) : studies by Gopalan and others have shown that amino acid imbalance caused by an excess of leucine is the cause of pellagra in both Jowar (sorghum) and maize eaters. Excess of Leucine appears to interfere in the conversion of Tryptophan to niacin.

i. Niacin is synthesized from Tryptophan

ii. 60 mg of Tryptophan, gives 1 mg equivalent of niacin. Active forms of Niacin, are NAD+ and NADP+

iii. Deficiency of Niacin (pellagra) Is due to: -

a. When maize (corn) used as stable food niacin is in fact present, but it is in a bound unavailable form.

b. Dependence on sorghum Pellagra in not because of Low tryptophan but because of high Leucine

c. content, that inhibit quinolinone phosphoribosyl transferase, a key enzyme in the conversion of tryptophan to Niacin (NAD+)

d. Deficiency of B6 (Pyridoxal phosphate also causes pellagra, as it acts as co-factor in pathway of

e. synthesis of niacin from Tryptophan. Isoniazid cause B6 deficiency there by pellagra.

f. Due to carcinoid syndrome Tryptophan metabolism is diverted into serotonin and in Hartnup disease Tryptophan absorption is impaired

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