Stabilizing Action of Tetrahydrobiopterin on the Activity of Neuronal Nitric Oxide Synthase

作者：Tsyvkin V N^*

来源：Neurophysiology, 2012, 44(5): 351-355.

DOI：10.1007/s11062-012-9305-x

• nitric oxide synthase (NOS)
• tetrahydrobiopterin
• cerebellum
• cytoplasmic fraction

We studied the effect of tetrahydrobiopterin (BH4), one of the co-factors of NO synthase (NOS), on the process of inactivation of this enzyme in a cytoplasmic fraction obtained from rat cerebellar tissue. Tetrahydrobiopterin stimulated in a dose-dependent manner the activity of NOS measured according to accumulation of [H-3]-citrulline. In the course of reaction at 37 degrees C without the addition of BH4, the enzymatic activity rapidly decreased; in the presence of 10 mu M BH4, the rate of inactivation of NOS was noticeably smaller. Preincubation (40 min long) under the same conditions but in the absence of substrates (arginine and NADPH) and BH4 also led to a decrease in the enzymatic activity. Preincubation in the presence of 1 mM BH4 not only slowed down inactivation of NOS but also provided an appreciable increase in its activity, as compared with the variant without preincubation. This fact is indicative of the presence of a BH4-free inactive form of the above-mentioned enzyme in the cytoplasmic fraction, which can be additionally activated. The obtained data show that BH4 stabilizes the activity of NOS due to a decrease in the rate of inactivation of this enzyme occurring independently of realization of the enzymatic reaction.

• 出版日期2012-11