Elucidation of Prorerties and Physiological Roles of nicoinamide-Biding Protein, and It's Applocation to the Determination of Vitamin

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Various vinding proteins (BP) specific to each vitamin are kyown, but the BP specific to free nicotinic acid(NiA) or free nicotinamide (NAm) is not known. Accordingly we investigated such protein and finally we have just found NAm specific BP (NAm-BP). Hence various properties of this protein in hog liveer and in various organs in rat, and effects of niacin-related compounds were investigated. As the results, followings are confirmed.After the experimental diets of NAm-deficient, control, and excess NAm are fed to rats for 2 weeks ad libitum, the activities of NAm-BP were determined. the activities in almost all organs including liver and kidney were higher than those in organs of control group. It is suggested that the ability of NAm binding of NAm-BP is changed according to the amount of NAm in bodies. Cogactor for the binding was also found in the extract from hog liver and the properties of it were as follows : molecular weight, less than 10000 ; stability, heat stable ; acid and aldali labile ; charge, neutral. Exchange of NAm on NAm-BP was obseved when exess NAm was added. NAm-bindin ability was greately lowered with MNA and 2-Py. As these compounds were excreted in urine as final products from NAm catabolism, it is suggested tha NAm is supplied according to the decrease of NAm in the body.Application of this NAm-BP to the determination of vitamin could not be done, because of shortage of time.