Stereo- and regiospecificity of yeast phytases-chemical synthesis and enzymatic conversion of the substrate analogues neo- and L-chiro-inositol hexakisphosphate.
Phytases are enzymes that catalyze the hydrolysis of phosphate esters in myo-inositol hexakisphosphate (phytic acid). The precise routes of enzymatic dephosphorylation by phytases of the yeast strains Saccharomyces cerevisiae and Pichia rhodanensis have been investigated up to the myo-inositol trisphosphate level, including the absolute configuration of the intermediates. Stereoselective assignment of the myo-inositol pentakisphosphates (D-myo-inositol 1,2,4,5,6-pentakisphosphate and D-myo-inositol 1,2,3,4,5-pentakisphosphate) generated was accomplished by a new method based on enantiospecific enzymatic conversion and HPLC analysis. Via conduritol B or E derivatives the total syntheses of two epimers of myo-inositol hexakisphosphate, neo-inositol hexakisphosphate and L-chiro-inositol hexakisphosphate were performed to examine the specificity of the yeast phytases with these substrate analogues. A comparison of kinetic data and the degradation pathways determined gave the first hints about the molecular recognition of inositol hexakisphosphates by the enzymes. Exploitation of the high stereo- and regiospecificity observed in the dephosphorylation of neo- and L-chiro-inositol hexakisphosphate made it possible to establish enzyme-assisted steps for the synthesis of D-neo-inositol 1,2,5,6-tetrakisphosphate, L-chiro-inositol 1,2,3,5,6-pentakisphosphate and L-chiro-inositol 1,2,3,6-tetrakisphosphate.
Adelt
Stephan
S
Institut für Biochemie, Fachbereich 9-Chemie, Bergische Universität Wuppertal, Gaussstrasse 20, 42097 Wuppertal, Germany.
Podeschwa
Michael
M
Dallmann
Guido
G
Altenbach
Hans-Josef
HJ
Vogel
Günter
G
D010832:6-Phytase / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D006868:Hydrolysis; D008956:Models, Chemical; D008958:Models, Molecular; D010833:Phytic Acid / Q000031:analogs & derivatives / Q000737:chemistry* / Q000378:metabolism*; D010843:Pichia / Q000737:chemistry / Q000145:classification / Q000201:enzymology*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology*; D012680:Sensitivity and Specificity; D013045:Species Specificity; D013237:Stereoisomerism; D013379:Substrate Specificity
D010833:Phytic Acid; D010832:6-Phytase