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cDNA encoding a hormone- and guanine nucleotide-stimulated adenylyl cyclase ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1 (type 6) from rat liver and kidney has been cloned and expressed. This enzyme is stimulated by forskolin, guanosine 5'-gamma-thiotriphosphate, and isoproterenol plus GTP but is not stimulated by beta gamma subunits of guanine nucleotide-binding proteins. A second form (type 5), which is 75% similar to type 6, has also been cloned. Both types 5 and 6 cDNAs have multiple messages. PCR-based detection of the mRNA for the type 5 and 6 enzymes indicates that both are widely distributed. Homology analyses indicate at least four distinct subfamilies of guanine nucleotide stimulatory protein-regulated adenylyl cyclases. Types 5 and 6 enzymes define one distinct subfamily of mammalian adenylyl cyclases. Diversity of one guanine nucleotide-binding protein-regulated effector may allow different modes of regulation of cell-surface signal transmission.
Premont et al. (Thu,) studied this question.