Nitric oxide synthase (NOS) activity is found both in soluble and in p
articulate fractions of the carp brain. The K-m values for arginine ar
e 2.8 +/- 0.5 and 3.3 +/- 0.4 mu M for the soluble and particulate fra
ctions, respectively. K-i for N-G-monomethyl-L-arginine inhibitor are
2.6 +/- 0.5 and 2.9 +/- 0.6 mu M, and activation energy for the breakd
own of the substrate-enzyme complex 8120 +/- 710 and 4620 +/- 450 cal
per mole. Carp enzyme shows higher affinity than rat NOS for Ca2+ and
for the competitive inhibitor 7-nitroindazole. (C) 1998 Elsevier Scien
ce Ireland Ltd.