1hm7: Difference between revisions

[[Image:1hm7.gif|left|200px]]<br /><applet load="1hm7" size="350" color="white" frame="true" align="right" spinBox="true"  

Incubation of farnesyl diphosphate (1) with the W308F or W308F/H309F mutants of pentalenene synthase, an enzyme from Streptomyces UC5319, yielded pentalenene (2), accompanied by varying proportions of (+)-germacrene A (7) with relatively minor changes in k(cat) and k(cat)/K(m). By contrast, single H309 mutants gave rise to both (+)-germacrene A (7) and protoilludene (8) in addition to pentalenene (2). Mutation to glutamate of each of the three aspartate residues in the Mg(2+)-binding aspartate-rich domain, (80)DDLFD, resulted in reduction in the k(cat)/K(m) for farnesyl diphosphate and formation of varying proportions of pentalenene and (+)-germacrene A (7). Formation of (+)-germacrene A (7) by the various pentalenene synthase mutants is the result of a derailment of the natural anti-Markovnikov cyclization reaction, and not simply the consequence of trapping of a normally cryptic, carbocationic intermediate. Both the N219A and N219L mutants of pentalenene synthase were completely inactive, while the corresponding N219D mutant had a k(cat)/K(m) which was 3300-fold lower than that of the wild-type synthase, and produced a mixture of pentalenene (2) (91%) and the aberrant cyclization product beta-caryophyllene (9) (9%). Finally, the F77Y mutant had a k(cat)/K(m) which was reduced by 20-fold compared to that of the wild-type synthase.

1HM7 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Streptomyces_sp. Streptomyces sp.]. Active as [http://en.wikipedia.org/wiki/Pentalenene_synthase Pentalenene synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.2.3.7 4.2.3.7] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1HM7 OCA].  

[[Category: Cane, D E.]]

[[Category: Christianson, D W.]]

[[Category: Paschall, C M.]]

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