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KMID : 0376219740110010269
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Chonnam Medical Journal
1974 Volume.11 No. 1 p.269 ~ p.279
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Studies on NAD Glycohydrolase in Rabbit Leucocytes
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Abstract
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Rabbit polymorphonuclear leucocytes obtained from the peritoneal exudate were sonicated in the presence of deoxycholate to produce a homogeneous granule suspension. And some properties of NAD glycohydrolase ?(NADase) in the granule suspension were investigated.
Sonic treatment of the leucocyte suspension in the presence of 0.26% Nadeoxycholate resulted in 1. 3-fold increase in NADase activity with the establishment of almost linear time-course hydrolysis of NAD, indicating a partial solubilizationx of the leucocyte NADase.
The enzyme showed optimal pH around 6.0, and its apparent Michaelis constant for NAD was 10 mM. Although the enzyme catalyzed the hydrolysis of NADP and nicotinamide mononucleotide, their hydrolytic rates were low at pff 6.0 and pH 7.4 as compared with the rate of NAD hydrolysis.
Nicotinamide at a concentration of 3 mM caused 50 % inhibition of the enzyme
activity. The enzyme was also markedly inhibited by isonicotinic acid hydrazide (INH) at low concentrations. Nevertheless, it could catalyze the formation of INH analogue of NAD.
The enzyme was also inhibited by nicotinic acid and 3-acetylpyridine at higher concentrations, or by some metal ions.
Urea, which was reported to cause an activation of rabbit erythrocyte NADaseat low concentrations, could not activate the, leucocyte NADase, and rather inhibited the activity at 4 M concentration.
By comparison with the hitherto-reported properties of rabbit erythrocyte-NADase, it can be concluded that rabbit leucocyte NADase is distinct from the erythrocyte NADase.
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