1eli: Difference between revisions

==Overview==

Monomeric sarcosine oxidase (MSOX) is an inducible bacterial flavoenzyme, that catalyzes the oxidative demethylation of sarcosine (N-methylglycine), and contains covalently bound FAD [8alpha-(S-cysteinyl)FAD]. This paper, describes the spectroscopic and thermodynamic properties of MSOX as well, as the X-ray crystallographic characterization of three new, enzyme.inhibitor complexes. MSOX stabilizes the anionic form of the, oxidized flavin (pK(a) = 8.3 versus 10.4 with free FAD), forms a, thermodynamically stable flavin radical, and stabilizes the anionic form, of the radical (pK(a) < 6 versus pK(a) = 8.3 with free FAD). MSOX forms a, covalent flavin.sulfite complex, but there appears to be a significant, kinetic barrier against complex formation. Active site binding, determinants were probed in thermodynamic studies with various substrate, analogues whose binding was found to perturb the flavin absorption, spectrum and inhibit MSOX activity. The carboxyl group of sarcosine is, essential for binding since none is observed with simple amines. The amino, group of sarcosine is not essential, but binding affinity depends on the, nature of the substitution (CH(3)XCH(2)CO(2)(-), X = CH(2) < O < S < Se <, Te), an effect which has been attributed to differences in the strength of, donor-pi interactions. MSOX probably binds the zwitterionic form of, sarcosine, as judged by the spectrally similar complexes formed with, dimethylthioacetate [(CH(3))(2)S(+)CH(2)CO(2)(-)] and dimethylglycine, (K(d) = 20.5 and 17.4 mM, respectively) and by the crystal structure of, the latter. The methyl group of sarcosine is not essential but does, contribute to binding affinity. The methyl group contribution varied from, -3.79 to -0.65 kcal/mol with CH(3)XCH(2)CO(2)(-) depending on the nature, of the heteroatom (NH(2)(+) > O > S) and appeared to be inversely, correlated with heteroatom electron density. Charge-transfer complexes are, formed with MSOX and CH(3)XCH(2)CO(2)(-) when X = S, Se, or Te. An, excellent linear correlation is observed between the energy of the charge, transfer bands and the one-electron reduction potentials of the ligands., The presence of a sulfur, selenium, or telurium atom identically, positioned with respect to the flavin ring is confirmed by X-ray, crystallography, although the increased atomic radius of S < Se < Te, appears to simultaneously favor an alternate binding position for the, heavier atoms. Although L-proline is a poor substrate, aromatic, heterocyclic carboxylates containing a five-membered ring and various, heteroatoms (X = NH, O, S) are good ligands (K(d, X=NH) = 1.37 mM) and, form charge-transfer complexes with MSOX. The energy of the, charge-transfer bands (S > O >> NH) is linearly correlated with the, one-electron ionization potentials of the corresponding heterocyclic, rings.

==About this Structure==

1ELI is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_sp. Bacillus sp.] with PO4, CL, FAD and PYC as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Sarcosine_oxidase Sarcosine oxidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.5.3.1 1.5.3.1] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1ELI OCA].

 

Monomeric sarcosine oxidase: 1. Flavin reactivity and active site binding determinants., Wagner MA, Trickey P, Chen ZW, Mathews FS, Jorns MS, Biochemistry. 2000 Aug 1;39(30):8813-24. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=10913292 10913292]

[[Category: Bacillus sp.]]

[[Category: Sarcosine oxidase]]

[[Category: Single protein]]

[[Category: Chen, Z.W.]]

[[Category: Jorns, M.S.]]

[[Category: Mathews, F.S.]]

[[Category: Trickey, P.]]

[[Category: Wagner, M.A.]]