1hb4
From Proteopedia
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==Overview== | ==Overview== | ||
| - | BACKGROUND: Isopenicillin N synthase (IPNS) catalyses formation of | + | BACKGROUND: Isopenicillin N synthase (IPNS) catalyses formation of bicyclic isopenicillin N, precursor to all penicillin and cephalosporin antibiotics, from the linear tripeptide delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine. IPNS is a non-haem iron(II)-dependent enzyme which utilises the full oxidising potential of molecular oxygen in catalysing the bicyclisation reaction. The reaction mechanism is believed to involve initial formation of the beta-lactam ring (via a thioaldehyde intermediate) to give an iron(IV)-oxo species, which then mediates closure of the 5-membered thiazolidine ring. RESULTS: Here we report experiments employing time-resolved crystallography to observe turnover of an isosteric substrate analogue designed to intercept the catalytic pathway at an early stage. Reaction in the crystalline enzyme-substrate complex was initiated by the application of high-pressure oxygen, and subsequent flash freezing allowed an oxygenated product to be trapped, bound at the iron centre. A mechanism for formation of the observed thiocarboxylate product is proposed. CONCLUSIONS: In the absence of its natural reaction partner (the N-H proton of the L-cysteinyl-D-valine amide bond), the proposed hydroperoxide intermediate appears to attack the putative thioaldehyde species directly. These results shed light on the events preceding beta-lactam closure in the IPNS reaction cycle, and enhance our understanding of the mechanism for reaction of the enzyme with its natural substrate. |
==About this Structure== | ==About this Structure== | ||
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[[Category: Emericella nidulans]] | [[Category: Emericella nidulans]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Adlington, R | + | [[Category: Adlington, R M.]] |
| - | [[Category: Baldwin, J | + | [[Category: Baldwin, J E.]] |
| - | [[Category: Burzlaff, N | + | [[Category: Burzlaff, N I.]] |
| - | [[Category: Clifton, I | + | [[Category: Clifton, I J.]] |
| - | [[Category: Elkins, J | + | [[Category: Elkins, J M.]] |
| - | [[Category: Ogle, J | + | [[Category: Ogle, J M.]] |
| - | [[Category: Roach, P | + | [[Category: Roach, P L.]] |
| - | [[Category: Rutledge, P | + | [[Category: Rutledge, P J.]] |
[[Category: FE2]] | [[Category: FE2]] | ||
[[Category: SCV]] | [[Category: SCV]] | ||
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[[Category: penicillin biosynthesis]] | [[Category: penicillin biosynthesis]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:59:27 2008'' |
Revision as of 10:59, 21 February 2008
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ISOPENICILLIN N SYNTHASE FROM ASPERGILLUS NIDULANS (OXYGEN EXPOSED PRODUCT FROM ANAEROBIC ACOV FE COMPLEX)
Overview
BACKGROUND: Isopenicillin N synthase (IPNS) catalyses formation of bicyclic isopenicillin N, precursor to all penicillin and cephalosporin antibiotics, from the linear tripeptide delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine. IPNS is a non-haem iron(II)-dependent enzyme which utilises the full oxidising potential of molecular oxygen in catalysing the bicyclisation reaction. The reaction mechanism is believed to involve initial formation of the beta-lactam ring (via a thioaldehyde intermediate) to give an iron(IV)-oxo species, which then mediates closure of the 5-membered thiazolidine ring. RESULTS: Here we report experiments employing time-resolved crystallography to observe turnover of an isosteric substrate analogue designed to intercept the catalytic pathway at an early stage. Reaction in the crystalline enzyme-substrate complex was initiated by the application of high-pressure oxygen, and subsequent flash freezing allowed an oxygenated product to be trapped, bound at the iron centre. A mechanism for formation of the observed thiocarboxylate product is proposed. CONCLUSIONS: In the absence of its natural reaction partner (the N-H proton of the L-cysteinyl-D-valine amide bond), the proposed hydroperoxide intermediate appears to attack the putative thioaldehyde species directly. These results shed light on the events preceding beta-lactam closure in the IPNS reaction cycle, and enhance our understanding of the mechanism for reaction of the enzyme with its natural substrate.
About this Structure
1HB4 is a Single protein structure of sequence from Emericella nidulans with , and as ligands. Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
Alternative oxidation by isopenicillin N synthase observed by X-ray diffraction., Ogle JM, Clifton IJ, Rutledge PJ, Elkins JM, Burzlaff NI, Adlington RM, Roach PL, Baldwin JE, Chem Biol. 2001 Dec;8(12):1231-7. PMID:11755401
Page seeded by OCA on Thu Feb 21 12:59:27 2008
