Activity and Stability of .ALPHA.- and .BETA.-Mannosyltransferases in Candida albicans Cells Cultured at High Temperature and at Low pH

We measured the activity and stability of three mannosyltransferases to ascertain the mechanisms of changes in the antigenicity and the mannan structure of Candida albicans cells cultured at high temperature (37 degrees C) under acidic (pH 2.0) conditions in a liquid medium. The alpha-1,6-mannosyltransferase (alpha-1,6-MT) activity of the particulate-insoluble enzyme fractions prepared from C. albicans J-1012 (J-1012) cells cultured at 37 degrees C was retained compared to those at 27 degrees C, whereas beta-1,2-mannosyltransferase II (beta-1,2-MT II) activity was detected in the 27 degrees C fraction but not in the 37 degrees C fraction. Similar results were obtained in the fraction prepared from J-1012 cells cultured at pH 2.0. The alpha-1,6-MT activities of fractions prepared from C. albicans NIH B-792 (B-792) strain cells cultured at 37 degrees C were retained compared to those at 27 degrees C, whereas beta-1,2-mannosyltransferase VI-6 (beta-1,2-MT VI-6) activity was detected in the fraction of B-792 cells cultured at 27 degrees C but not detected in the 37 degrees C fraction. We also found that the beta-1,2-MT II and beta-1,2-MT VI-6 activity of C. albicans cells was more sensitive to both high temperature and low pH compared with alpha-1,6-MT activity.