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GUANYLATE CYCLASES IN CNS: ENZYMATIC CHARACTERISTICS OF SOLUBLE AND PARTICULATE ENZYMES FROM MOUSE CEREBELLUM AND RETINA
Author(s) -
Troyer Edward W.,
Hall Isabelle A.,
Ferrendelli James A.
Publication year - 1978
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1978.tb00117.x
Subject(s) - gucy1b3 , gucy1a3 , gtp' , gucy2d , biochemistry , enzyme , chemistry , retina , guanylate cyclase , cerebellum , guanylate cyclase 2c , biology , endocrinology , neuroscience
Guanylate cyclase activity is present in both soluble and particulate fractions of homogenates of mouse cerebellum and retina. Soluble guanylate cyclases in cerebellum and retina have an apparent K m for GTP of approx 40 and 70 μM, respectively; are stimulated by Ca 2+ and Mg 2+ in the presence of low Mn 2+ ; and do not respond to NaN 3 , NH 2 OH or detergent. The particulate guanylate cyclase found in brain has an apparent K m GTP of 237 7mu;M, is not stimulated by Ca 2+ or Mg 2+ in the presence of low Mn 2+ , but is stimulated by NaN 3 , NH 2 OH, and detergent. In particulate fractions of normal retina, guanylate cyclase has two apparent K m GTP values (42 and 225 μM); has higher activity at low concentrations of Mn 2+ (0.5 mM) than at high concentrations (5.0 mM); is inhibited by Ca 2+ ; and does not respond to NaN 3 , NH 2 OH, or detergent. Retinas essentially devoid of photoreceptor cells (from mice with photoreceptor dystrophy) have soluble guanylate cyclase activity which is similar to that in normal retina, but have only 4% as much particulate guanylate cyclase activity. This residual particulate guanylate cyclase has an apparent K m GTP value of 392 μM and other properties similar to particulate guanylate cyclase from brain. These data indicate the presence of three distinguishable guanylate cyclases in CNS: (1) a soluble enzyme present in both brain and retina: (2) a particulate enzyme which is also present in brain and in the inner or neural retina: and (3) another particulate enzyme which is apparently unique and confined to retinal photoreceptor cells.