Open AccessIdentification of a salvage pathway for D ‐arabinose in Mycobacterium smegmatis
Author(s) -
WOJTKIEWICZ Beata,
SZMIDZINSKI Ryszard,
JEZIERSKA Anna,
COCITO Carlo
Publication year - 1988
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1988.tb13873.x
Subject(s) - arabinose , arabitol , biochemistry , mycobacterium smegmatis , dehydrogenase , glycerol , ribitol , nad+ kinase , xylitol , bacteria , chemistry , oxidoreductase , enzyme , sorbitol , xylose , biology , fermentation , mycobacterium tuberculosis , medicine , tuberculosis , pathology , genetics
Extracts of Mycobacterium smegmatis , which was adapted to growth in synthetic medium containing D ‐arabinose as sole carbon source, catalyzed the NADPH‐mediated reduction of D ‐arabinose to D ‐arabitol. When arabinose‐adapted bacteria were transferred to glycerol medium, resumption of growth was accompanied by a sharp drop in the specific activity of this enzyme. Moreover, extracts of cells grown in D ‐arabinose medium contained large amounts of an NAD + ‐linked pentitol dehydrogenase, as compared to bacteria multiplying in glycerol medium. The specific activity of mycobacterial extracts was tenfold higher for D ‐arabitol than for its L ‐isomer, and eightfold higher than for xylitol (it was more than fortyfold lower in the case of glycerol‐grown cells). The product of the pentitol dehydrogenase reaction was identified as D ‐xylulose by three different procedures. On the basis of these data, it is suggested that utilization of exogenous D ‐arabinose in mycobacteria involves two dehydrogenases that catalyze the reactions D ‐arabinose D ‐arabitol D ‐xylulose, by virtue of which an aldopentose is converted into a ketopentose. The alditol: NADP oxidoreductase was isolated from homogenates of D ‐arabinose‐adapted mycobacteria, and purified by DEAE‐cellulose chromatography. The enzymatic activity was restricted to a single band which, under denaturing conditions, comigrated with albumin (∼ 46 kDa). It was insensitive to 2‐mercaptoethanol, EDTA and NaF, and was inactivated at 70°C.