title: Hydrogen sulfide stimulates the catalytic activity of a heme-regulated phosphodiesterase from Escherichia coli (Ec DOS).
abstract: Ec DOS, a heme-regulated phosphodiesterase from Escherichia coli, is an oxygen sensor enzyme composed of a heme-bound O(2) sensor domain at the N-terminus and a catalytic domain at the C-terminus. The catalytic activity of Ec DOS is substantially enhanced with the formation of a Fe(II) heme-O(2) complex. The physiological importance of H(2)S as a fourth signaling gas molecule in addition to O(2), CO and NO is an emerging focus of research, since H(2)S participates in various physiological functions. In the present study, we showed that catalysis by Ec DOS is markedly increased by H(2)S under aerobic conditions. Absorption spectral findings suggest that SH(-)-modified heme iron complexes, such as Fe(III)-SH(-) and Fe(II)-O(2) complexes, represent the active species for H(2)S-induced catalysis. We further examined the role of Cys residues in H(2)S-induced catalysis using Cys→Ala mutant enzymes. Based on the collective data, we speculate that H(2)S-induced catalytic enhancement is facilitated by an admixture of Fe(III)-SH(-) and Fe(II)-O(2) complexes formed during catalysis and modification of specific Cys residue(s) in the catalytic domain.
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Sendai 980-8577, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Takahashi
authors.forename: Madoka
authors.initials: M
authors.lastname: Sekimoto
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tanaka
authors.forename: Atsunari
authors.initials: A
authors.lastname: Tanaka
authors.forename: Jotaro
authors.initials: J
authors.lastname: Igarashi
authors.forename: Toru
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D002384:Catalysis; D006152:Cyclic GMP / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D006418:Heme / Q000378:metabolism*; D006862:Hydrogen Sulfide / Q000494:pharmacology*; D016297:Mutagenesis, Site-Directed; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D006418:Heme; D010727:Phosphoric Diester Hydrolases; D006152:Cyclic GMP; D006862:Hydrogen Sulfide