9 Other Deoxy Sugar Aldolases

Abstract

Publisher Summary This chapter focuses on enzymes, which catalyze the reversible cleavage of deoxy sugars. These include L-rhamnulose 1-phosphate aldolase and L-fuculose 1-phosphate aldolase, which resemble classic fructoisediphosphate aldolase as dihydroxyacetone phosphate (DHAP) and an aldehyde are produced by cleavage of a 6-deoxyketoliexose 1-phosphate. Deoxyribose-5-phosphate aldolase on the other hand, differs in that two aldehydes–acetaldehyde and glyceraldehyde 3-phosphate– are produced by cleavage of a 2-deoxyaldopentose-5-phosphate. Nevertheless, deoxyribose-5-phosphate aldolase is a true aldolase and shares many features with the classic examples of this class of enzymes. L-rhamnulose 1-phosphate aldolase has been demonstrated in E. coli and L. plantarum. Formation of L-rhamnulose 1-phosphate can be considered presumptive evidence for the presence of the aldolase in these organisms is well as in P. pestis. L-Rhamnulose 1-phosphate aldolase is present in sonicates of L-rhamnose-grown E. coli K-12 or of a constitutive mutant grown without inducer. The enzyme is purified by a procedure involving treatment with MnCl2, fractionation with ammonium sulfate, acetone fractionation, Sephadex G-100 and DEAE-Sephadex chromatography, precipitation with ammonium sulfate, and crystallization from an ammonium sulfate solution. L-Rhamnulose l-phosphate aldolase contains one component of mobility corresponding to a molecular weight of 135,000 when chromatographed on a thin layer of Sephadex G-200.