title: Stereochemical retention of the configuration in the action of Fhit on phosphorus-chiral substrates.
abstract: Fhit is the protein product of FHIT, a candidate human tumor suppressor gene. Fhit catalyzes the hydrolysis of diadenosine triphosphate (Ap3A) to AMP and ADP. Fhit is here shown to catalyze the hydrolysis in H218O with production of adenosine 5'-[18O]phosphate and ADP, proving that the substitution of water is at Palpha and not at Pbeta. The chain fold of Fhit is similar to that of galactose-1-phosphate uridylyltransferase, which functions by a double-displacement mechanism through the formation of a covalent nucleotidyl-enzyme intermediate and overall retention of configuration at Palpha. The active site of Fhit contains a histidine motif that is reminiscent of the HPH motif in galactose-1-phosphate uridylyltransferases, in which the first histidine residue serves as the nucleophilic catalyst to which the nucleotidyl group is bonded covalently in the covalent intermediate. In this work, the Fhit-catalyzed cleavage of (RP)- and (SP)-gamma-(m-nitrobenzyl) adenosine 5'-O-1-thiotriphosphate (mNBATPalphaS) in H218O to adenosine 5'-[18O]thiophosphate is shown to proceed with overall retention of configuration at phosphorus. gamma-(m-Nitrobenzyl) adenosine 5'-O-triphosphate (mNBATP) is approximately as good a substrate for Fhit as Ap3A, and both (RP)- and (SP)-mNBATPalphaS are substrates that react at about 0.5% of the rate of Ap3A. The stereochemical evidence indicates that hydrolysis by Fhit proceeds by a double-displacement mechanism, presumably through a covalent AMP-enzyme intermediate.
authors: Institute for Enzyme Research, The Graduate School, and Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA.
authors: A
authors: A
authors: Abend
authors: P N
authors: PN
authors: Garrison
authors: L D
authors: LD
authors: Barnes
authors: P A
authors: PA
authors: Frey
mesh_terms: D017766:Acid Anhydride Hydrolases; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D002384:Catalysis; D015226:Dinucleoside Phosphates / Q000378:metabolism; D016147:Genes, Tumor Suppressor; D006801:Humans; D006868:Hydrolysis; D009363:Neoplasm Proteins; D010758:Phosphorus / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism; D013379:Substrate Specificity; D000099170:Bis(5'-adenosyl)triphosphatase
chemical_list: D017766:Acid Anhydride Hydrolases; D000255:Adenosine Triphosphate; D015226:Dinucleoside Phosphates; D009363:Neoplasm Proteins; D010758:Phosphorus; D011506:Proteins; D000099170:Bis(5'-adenosyl)triphosphatase; C011440:diadenosine triphosphate