title: A novel calcium-dependent bacterial phosphatidylinositol-specific phospholipase C displaying unprecedented magnitudes of thio effect, inverse thio effect, and stereoselectivity.
abstract: Understanding the potential range of enzymatic thio effects (kO/kS) is of great value when using sulfur-substituted phosphate analogues to study phosphoryl transfer reactions in enzymes and ribozymes. Herein we report that a newly discovered Ca2+-dependent Streptomyces antibioticus phosphatidylinositol-specific phospholipase C and its mutants display unprecedented magnitudes of thio effect, inverse thio effect, and RP/SP stereoselectivity. We demonstrate that for a single enzyme the bridging thio effect can vary from 0.002 to 20 and the nonbridging thio effect can vary from 1 to 108. These values fall outside the range of those reported for nonenzymatic reactions, emphasizing the need for cautious interpretation when using thio effects to elucidate details of enzyme catalysis.
authors.affiliation: Departments of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Zhao
authors.forename: Yinghui
authors.initials: Y
authors.lastname: Liu
authors.forename: Karol S
authors.initials: KS
authors.lastname: Bruzik
authors.forename: Ming-Daw
authors.initials: MD
authors.lastname: Tsai
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D054803:Phospholipase C delta; D013237:Stereoisomerism; D013303:Streptomyces antibioticus / Q000201:enzymology*; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000378:metabolism*; D010738:Type C Phospholipases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D007527:Isoenzymes; D013438:Sulfhydryl Compounds; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; D054803:Phospholipase C delta; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D002118:Calcium