1ely: Difference between revisions
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'''E. COLI ALKALINE PHOSPHATASE MUTANT (S102C)''' | '''E. COLI ALKALINE PHOSPHATASE MUTANT (S102C)''' | ||
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[[Category: Nolte, M.]] | [[Category: Nolte, M.]] | ||
[[Category: Stec, B.]] | [[Category: Stec, B.]] | ||
[[Category: | [[Category: Alkaline phosphatase]] | ||
[[Category: | [[Category: Hydrolase]] | ||
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Revision as of 15:15, 2 May 2008
E. COLI ALKALINE PHOSPHATASE MUTANT (S102C)
OverviewOverview
Escherichia coli alkaline phosphatase (EC 3.1.3.1) is a non-specific phosphomonoesterase that catalyzes the hydrolysis reaction via a phosphoseryl intermediate to produce inorganic phosphate and the corresponding alcohol. We investigated the nature of the primary nucleophile, fulfilled by the deprotonated Ser102, in the catalytic mechanism by mutating this residue to glycine, alanine and cysteine. The efficiencies of the S102G, S102A and S102C enzymes were 6 x 10(5)-fold, 10(5)-fold and 10(4)-fold lower than the wild-type enzyme, respectively, as measured by the kcat/Km ratio, still substantially higher than the non-catalyzed reaction. In order to investigate the structural details of the altered active site, the enzymes were crystallized and their structures determined. The enzymes crystallized in a new crystal form corresponding to the space group P6322. Each structure has phosphate at each active site and shows little departure from the wild-type model. For the S102G and S102A enzymes, the phosphate occupies the same position as in the wild-type enzyme, while in the S102C enzyme it is displaced by 2.5 A. This kinetic and structural study suggests an explanation for differences in catalytic efficiency of the mutant enzymes and provides a means to study the nature and strength of different nucleophiles in the same environment. The analysis of these results provides insight into the mechanisms of other classes of phosphatases that do not utilize a serine nucleophile.
About this StructureAbout this Structure
1ELY is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
Kinetic and X-ray structural studies of three mutant E. coli alkaline phosphatases: insights into the catalytic mechanism without the nucleophile Ser102., Stec B, Hehir MJ, Brennan C, Nolte M, Kantrowitz ER, J Mol Biol. 1998 Apr 3;277(3):647-62. PMID:9533886 Page seeded by OCA on Fri May 2 15:15:45 2008