Polyol Dehydrogenases in Candida Albicans

Abstract

Candida albicans grown in a liquid medium containing 0.5% D-xylose produced an adaptative NADP-polyol dehydrogenase which catalyzes the reversible reduction of some aldoses to the corresponding polyols. This enzyme was extracted from the culture and purified 134-fold using ammonium sulfate precipitations followed by calcium phosphate gel column chromatography. The Michaelis constant for D-xylose was determined to be 6.7 X 10 M. Heating of the enzyme up to 43° enhanced its activity, but it became completely inactive at 65°.The respective reduction of D-xylose and L-arabinose to xylitol and Larabitol by an NADP-linked enzyme was found by VEIGA et al.(1-4) in cellfree extracts of Candida albicans grown in the presence of D-xylose. Reports from CHIANG and KNIGHT (5) and HERS (6), on the other hand, involved aldose reductases respectively from filamentous fungus and seminal vesicle. MORET and SPERTI (7) showed the presence of a similar enzyme in Oospora lactis.The enzymatic oxidation of xylitol to D-xylulose by a non-specific NADlinked polyol dehydrogenase was also found in Candida albicans by VEIGA et al. (1-4). CHAKRAVORTY et al. (8) determined a similar enzyme in C. utilis, and CHIANG and KNIGHT (5) in a filamentous fungus. FOSSIT et al. (9) presented the data which indicates that Aerobacter aerogenes metabolizes xylitol through the route common to the other organisms, but a different sequence is involved in the metabolism of L-arabitol.Two xylitol dehydrogenases were determined by HOLLMANN and TOUSTER (10) and by HICKMAN Abbreviations: (NADP and NADPH) Nicotinamide adenine dinucleotide phosphate and its reduced form. (NAD and NADH) nicotinamide adenine dinucleotide and its reduced form.

Comparing the xylose reductase/xylitol dehydrogenase and xylose isomerase pathways in arabinose and xylose fermenting Saccharomyces cerevisiae strains

“…Arabitol is then re-oxidised by arabitol dehydrogenase to give L-xylulose [17], which is in turn converted to xylitol by L-xylulose reductase [17]. Xylitol is finally converted to xylulose by xylitol dehydrogenase (XDH) [18,19], whose activity is also part of xylose utilisation pathways (Figure 1). …”

“…In pentose-growing yeasts, xylose is first reduced by xylose reductase (XR) to xylitol [20], which in turn is oxidised to xylulose by XDH (Figure 1) [18,19]. In bacteria and some anaerobic fungi, xylose isomerase (XI) is responsible for direct conversion of xylose to xylulose [21-23] (Figure 1).…”

Identification and characterization of a novel pathway for aldopentose degradation in Acinetobacter baumannii

“…Xylitol is the convergence point of the merging L‐arabinose and D‐xylose utilization pathways, as D‐xylose is reduced to xylitol by the D‐xylose reductase. However, xylitol is then oxidized to D‐xylulose by the xylitol dehydrogenase and further phosphorylated by the xylulokinase, resulting in D‐xylulose‐5‐phosphate (Chiang & Knight, 1960; Veiga, 1968a, 1968b).…”

“…Ribulose-5-phosphate and D-xylose-5phosphate are further degraded in the pentose phosphate pathway (Hope et al, 1986;Skinner & Cooper, 1971). (Chiang & Knight, 1960;Veiga, 1968aVeiga, , 1968b.…”