Phosphorothioate Analogs of Phosphatidylinositol and Inositol 1,2-Cyclic Phosphate - Application to the Mechanism of Phospholipase-C

[[sponsorship]]基因體研究中心,生物化學研究所[[note]]已出版;有審查制度;不具代表性[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Drexel&SrcApp=hagerty_opac&KeyRecord=0097-6156&DestApp=JCR&RQ=IF_CAT_BOXPLOT[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=RID&SrcApp=RID&DestLinkType=FullRecord&DestApp=ALL_WOS&KeyUT=A1991FU0320001

Toward the mechanism of phosphoinositide-specific phospholipases C

[[sponsorship]]基因體研究中心,生物化學研究所[[note]]已出版;[SCI];有審查制度;不具代表性[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Drexel&SrcApp=hagerty_opac&KeyRecord=0968-0896&DestApp=JCR&RQ=IF_CAT_BOXPLO

Phospholipids chiral at phosphorus. Stereochemical mechanism for the formation of inositol 1-phosphate catalyzed by phosphatidylinositol-specific phospholipase C

[[sponsorship]]基因體研究中心,生物化學研究所[[note]]已出版;[SCI];有審查制度;不具代表性[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Drexel&SrcApp=hagerty_opac&KeyRecord=0006-2960&DestApp=JCR&RQ=IF_CAT_BOXPLOT[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=RID&SrcApp=RID&DestLinkType=FullRecord&DestApp=ALL_WOS&KeyUT=A1992HX9120001

Kinetic isotope effectsand stereochemical studies on a ribonuclease model: Hydrolysis reactions of uridine 3 \u27-pnitrophenylphosphate

The reactions of a ribonuclease model substrate, the compound uridine-3′-p-nitrophenyl phosphate, have been examined using heavy-atom isotope effects and stereochemical analysis. The cyclization of this compound is subject to catalysis by general base (by imidazole buffer), specific base (by carbonate buffer), and by acid. All three reactions proceed by the same mechanistic sequence, via cyclization to cUMP, which is stable under basic conditions but which is rapidly hydrolyzed to a mixture of 2′- and 3′-UMP under acid conditions. The isotope effects indicate that the specific base-catalyzed reaction exhibits an earlier transition state with respect to bond cleavage to the leaving group compared to the general base-catalyzed reaction. Stereochemical analysis indicates that both of the base-catalyzed reactions proceed with the same stereochemical outcome. It is concluded that the difference in the nucleophile in the two base-catalyzed reactions results in a difference in the transition state structure but both reactions are most likely concerted, with no phosphorane intermediate. The 15N isotope effects were also measured for the reaction of the substrate with ribonuclease A. The results indicate that considerably less negative charge develops on the leaving group in the transition state than for the general base-catalyzed reaction in solution