title: Identification and characterization of two unusual cGMP-stimulated phoshodiesterases in dictyostelium.
abstract: Recently, we recognized two genes, gbpA and gbpB, encoding putative cGMP-binding proteins with a Zn(2+)-hydrolase domain and two cyclic nucleotide binding domains. The Zn(2+)-hydrolase domains belong to the superfamily of beta-lactamases, also harboring a small family of class II phosphodiesterases from bacteria and lower eukaryotes. Gene inactivation and overexpression studies demonstrate that gbpA encodes the cGMP-stimulated cGMP-phosphodiesterase that was characterized biochemically previously and was shown to be involved in chemotaxis. cAMP neither activates nor is a substrate of GbpA. The gbpB gene is expressed mainly in the multicellular stage and seems to encode a dual specificity phosphodiesterase with preference for cAMP. The enzyme hydrolyses cAMP approximately 9-fold faster than cGMP and is activated by cAMP and cGMP with a K(A) value of approximately 0.7 and 2.3 microM, respectively. Cells with a deletion of the gbpB gene have increased basal and receptor stimulated cAMP levels and are sporogeneous. We propose that GbpA and GbpB hydrolyze the substrate in the Zn(2+)-hydrolase domain, whereas the cyclic nucleotide binding domains mediate activation. The human cGMP-stimulated cAMP/cGMP phosphodiesterase has similar biochemical properties, but a completely different topology: hydrolysis takes place by a class I catalytic domain and GAF domains mediate cGMP activation.
authors.affiliation: Department of Biochemistry, University of Groningen, 9747 AG Groningen, The Netherlands.
authors.forename: Leonard
authors.initials: L
authors.lastname: Bosgraaf
authors.forename: Henk
authors.initials: H
authors.lastname: Russcher
authors.forename: Helena
authors.initials: H
authors.lastname: Snippe
authors.forename: Sonya
authors.initials: S
authors.lastname: Bader
authors.forename: Joyce
authors.initials: J
authors.lastname: Wind
authors.forename: Peter J M
authors.initials: PJ
authors.lastname: Van Haastert
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004023:Dictyostelium / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D018390:Gene Targeting; D006801:Humans; D008969:Molecular Sequence Data; D010641:Phenotype; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D000242:Cyclic AMP; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D006152:Cyclic GMP