1h60: Difference between revisions

Pentaerythritol tetranitrate reductase (PETN reductase) degrades high, explosive molecules including nitrate esters, nitroaromatics and cyclic, triazine compounds. The enzyme also binds a variety of cyclic enones, including steroids; some steroids act as substrates whilst others are, inhibitors. Understanding the basis of reactivity with cyclic enones, requires structural information for the enzyme and key complexes formed, with steroid substrates and inhibitors. The crystal structure of oxidised, and reduced PETN reductase at 1.5 A resolution establishes a close, structural similarity to the beta/alpha-barrel flavoenzyme, old yellow, enzyme. In complexes of oxidised PETN reductase with progesterone (an, inhibitor), 1,4-androstadiene-3,17-dione and prednisone (both substrates), the steroids are stacked over the si-face of the flavin in an orientation, different from that reported for old yellow enzyme. The specifically, reducible 1,2 unsaturated bonds in 1,4-androstadiene-3,17-dione and, prednisone are not optimally aligned with the flavin N5 in oxidised enzyme, complexes. These structures suggest either relative "flipping" or shifting, of the steroid with respect to the flavin when bound in different redox, forms of the enzyme. Deuterium transfer from nicotinamide coenzyme to, 1,4-androstadiene-3,17-dione via the enzyme bound FMN indicates 1alpha, addition at the steroid C2 atom. These studies rule out lateral motion of, the steroid and indicate that the steroid orientation is "flipped" in, different redox states of the enzyme.

1H60 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Enterobacter_cloacae Enterobacter cloacae] with FMN and STR as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Sites: FMN and STR. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1H60 OCA].  

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