1,2-alpha-D-mannosidase from Penicillium citrinum: molecular and enzymic properties of two isoenzymes.
Two isoforms of acidic 1,2-alpha-D-mannosidases have been isolated from culture filtrate of Penicillium citrinum. The pI values of the two forms, designated 1,2-alpha-mannosidase Ia and Ib, were 4.6 and 4.7 respectively. Isoenzymes Ia and Ib exhibited the same molecular mass which was determined to be 53 kDa by SDS/PAGE and 54 kDa by gel-permeation chromatography. Enzymes Ia and Ib hydrolysed yeast mannan and 1,2-alpha-linked mannooligosaccharides, but did not hydrolyse p-nitrophenyl alpha-D-mannoside. The optimal pH for the hydrolysis of Man(alpha 1-->2)Man was 5.0 for both isoenzymes. Similar kinetic parameters were determined for the two forms. Activation energy was a little lower for Ia than Ib. There was little difference between the enzymes with regard to their performance at acidic or alkaline pH. The N-terminal amino acid sequences of the two enzymes were identical. Analysis of C-terminal peptides, which were prepared by tryptic digestion and anhydrotrypsin-agarose chromatography, showed that Ia and Ib had the same amino acid sequences in the C-terminal region. Tryptic digestion revealed a slight difference between the isoenzymes in the pattern of cleaved peptides on SDS/PAGE.
Yoshida
T
T
Department of Applied Biochemistry, Faculty of Agriculture, Tohoku University, Sendai, Japan.
Inoue
T
T
Ichishima
E
E
D000595:Amino Acid Sequence; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008361:Mannosidases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D010407:Penicillium / Q000201:enzymology*; D010449:Peptide Mapping; D013379:Substrate Specificity
D007527:Isoenzymes; D008361:Mannosidases; C046090:mannosyl-oligosaccharide 1,2-alpha-mannosidase