title: Characterization of cerebellar guanylate cyclase using N-methyl-N'-nitro-N-nitrosoguanidine. Presence of two different types of guanylate cyclase in soluble and particulate fractions.
abstract: Some characteristics of guanylate cyclase (GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2) in subcellular fractions prepared from rat cerebellum have been analyzed on the basis of responsiveness to N-methyl-N'-nitro-N-nitrosoguanidine and inhibitors related to N-nitroso compounds. The enzyme in 100 000 X g supernatant and crude mitochondrial (P2) fractions were differently activated (11- and 2.5-fold, respectively) by N-methyl-N'-nitro-N-nitrosoguanidine. The soluble fraction obtained by hypo-osmotic treatment and subsequent recentrifugation of the P2 (P2-soluble) contained a significantly higher total guanylate cyclase activity than that of the starting material (P2). The P2-soluble fraction also exhibited a lower responsiveness (1.5-fold) to N-methyl-N'-nitro-N-nitrosoguanidine than that found in the P2. The membrane fraction prepared from the P2 (P2-membrane) had no response to N-methyl-N'-nitro-N-nitrosoguanidine. Hemoglobin and vitamin A derivatives significantly inhibited both N-methyl-N'-nitro-N-nitrosoguanidine-activated 100 000 X g supernatant and basal P2-soluble enzyme activities, without effect on the basal activities in 100 000 X g supernatant and P2-membrane fractions. The present results suggest that two different types of guanylate cyclase may be present in rat cerebellum in terms of the responsiveness of N-nitroso compounds, and P2-soluble guanylate cyclase seems to be activated endogenously through a mechanism similar to the action of N-methyl-N'-nitro-N-nitrosoguanidine.
mesh_terms: D000818:Animals; D002531:Cerebellum / Q000201:enzymology*; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000378:metabolism*; D006454:Hemoglobins / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology*; D051381:Rats; D012995:Solubility; D013347:Subcellular Fractions / Q000201:enzymology; D013572:Synaptic Vesicles / Q000201:enzymology; D013696:Temperature; D014801:Vitamin A / Q000494:pharmacology
chemical_list: D006454:Hemoglobins; D014801:Vitamin A; D008769:Methylnitronitrosoguanidine; D006162:Guanylate Cyclase