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==Overview== | ==Overview== | ||
X-ray crystallographic studies of human alpha-thrombin with a novel, synthetic inhibitor, an acyl (alpha-aminoalkyl)phosphonate, reveal the, existence of a pentacovalent phosphorus intermediate state. Crystal, structures of the complex of alpha-thrombin with the phosphonate compound, were determined independently using crystals of different ages. The first, structure, solved from a crystal less than seven days old, showed a, pentacoordinated phosphorus moiety. The second structure, determined from, a crystal that was 12 weeks old, showed a tetracoordinated phosphorus, moiety. In the first structure, a water molecule, made nucleophilic by, coordination to His57 of alpha-thrombin, is bonded to the pentacoordinated, phosphorus atom. Its position is approximately equivalent to that occupied, by the water molecule responsible for hydrolytic deacylation during normal, hydrolysis. The pentacoordinated phosphorus adduct collapses to give the, expected pseudo tetrahedral complex, where the phosphorus atom is, covalently bonded to Ser195 O(gamma). The crystallographic data presented, here therefore suggest that the covalent bond formed between the, inhibitor's phosphorus atom and O(gamma) of Ser195 proceeds via an, addition-elimination mechanism, which involves the formation of a, pentacoordinate intermediate. | X-ray crystallographic studies of human alpha-thrombin with a novel, synthetic inhibitor, an acyl (alpha-aminoalkyl)phosphonate, reveal the, existence of a pentacovalent phosphorus intermediate state. Crystal, structures of the complex of alpha-thrombin with the phosphonate compound, were determined independently using crystals of different ages. The first, structure, solved from a crystal less than seven days old, showed a, pentacoordinated phosphorus moiety. The second structure, determined from, a crystal that was 12 weeks old, showed a tetracoordinated phosphorus, moiety. In the first structure, a water molecule, made nucleophilic by, coordination to His57 of alpha-thrombin, is bonded to the pentacoordinated, phosphorus atom. Its position is approximately equivalent to that occupied, by the water molecule responsible for hydrolytic deacylation during normal, hydrolysis. The pentacoordinated phosphorus adduct collapses to give the, expected pseudo tetrahedral complex, where the phosphorus atom is, covalently bonded to Ser195 O(gamma). The crystallographic data presented, here therefore suggest that the covalent bond formed between the, inhibitor's phosphorus atom and O(gamma) of Ser195 proceeds via an, addition-elimination mechanism, which involves the formation of a, pentacoordinate intermediate. | ||
==Disease== | |||
Known diseases associated with this structure: Dysprothrombinemia OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=176930 176930]], Hyperprothrombinemia OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=176930 176930]], Hypoprothrombinemia OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=176930 176930]] | |||
==About this Structure== | ==About this Structure== | ||
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[[Category: serine protease]] | [[Category: serine protease]] | ||
''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 12 17:14:00 2007'' | ||