Role of maltase in the utilization of sucrose by Candida albicans.
Two isoenzymes of maltase (EC 3.2.1.20) were purified to homogeneity from Candida albicans. Isoenzymes I and II were found to have apparent molecular masses of 63 and 66 kDa on SDS/PAGE with isoelectric points of 5.0 and 4.6 respectively. Both isoenzymes resembled each other in similar N-terminal sequence, specificity for the alpha(1-->4) glycosidic linkage and immune cross-reactivity on Western blots using a maltase II antigen-purified rabbit antibody. Maltase was induced by growth on sucrose whereas beta-fructofuranosidase activity could not be detected under similar conditions. Maltase I and II were shown to be unglycosylated enzymes by neutral sugar assay, and more than 90% of alpha-glucosidase activity was recoverable from spheroplasts. These data, in combination with other results from this laboratory [Geber, Williamson, Rex, Sweeney and Bennett (1992) J. Bacteriol. 174, 6992-6996] showing lack of a plausible leader sequence in genomic or mRNA transcripts, suggest an intracellular localization of the enzyme. To establish further the mechanism of sucrose assimilation by maltase, the existence of a sucrose-inducible H+/sucrose syn-transporter was demonstrated by (1) the kinetics of sucrose-induced [14C]sucrose uptake, (2) recovery of intact [14C]sucrose from ground cells by t.l.c. and (3) transport of 0.83 mol of H+/mol of [14C]sucrose. In total, the above is consistent with a mechanism whereby sucrose is transported into C. albicans to be hydrolysed by an intracellular maltase.
Williamson
P R
PR
Clinical Mycology Section, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD 20892.
Huber
M A
MA
Bennett
J E
JE
D000595:Amino Acid Sequence; D015153:Blotting, Western; D002176:Candida albicans / Q000201:enzymology*; D002236:Carbohydrate Conformation; D002851:Chromatography, High Pressure Liquid; D007526:Isoelectric Point; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D013379:Substrate Specificity; D013395:Sucrose / Q000378:metabolism*; D000520:alpha-Glucosidases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D007527:Isoenzymes; D013395:Sucrose; D000520:alpha-Glucosidases