Expression, crystallization and preliminary characterization of methylmalonyl coenzyme A epimerase from Propionibacterium shermanii

Methylmalonyl-CoA epimerase (MMCE) is an enzyme that interconverts the R an d S epimers of methylmalonyl-CoA in the pathway that links propionyl-CoA wi th succinyl-CoA. This is used for both biosynthetic and degradative process es, including the breakdown of odd-numbered fatty acids and some amino acid s. The enzyme has been expressed in Escherichia coli both as the native enz yme and as its selenomethionine (SeMet) derivative. Crystals of both forms have been obtained by vapour diffusion using monomethylether PEG 2000 as pr ecipitant. The native MMCE crystals are orthorhombic, with unit-cell parame ters a = 56.0, b = 114.0, c = 156.0 Angstrom, and the SeMet-MMCE crystals a re monoclinic, with unit-cell parameters a = 43.6, b = 78.6, c = 89.4 Angst rom, beta = 92.0 degrees; both diffract to better than 2.8 Angstrom resolut ion.