INVOLVEMENT OF TRANSGLUTAMINASE IN THE FORMATION OF COVALENT CROSS-LINKS IN THE CELL-WALL OF CANDIDA-ALBICANS

Activity of the enzyme glutaminyl-peptide-gamma-glutamylyl-transferase (EC 2.3.2.13; transglutaminase), which forms the interpeptidic cross- link N-epsilon-(gamma-glutamic)-lysine, was demonstrated in cell-free extracts obtained from both the yeast like and mycelial forms of Candi da albicans. Higher levels of enzymatic activity were observed in the cell wall fraction, whereas the cytosol contained only trace amounts o f activity. Cystamine, a highly specific inhibitor of the enzyme, was used to analyze a possible role of transglutaminase in the organizatio n of the cell wall structure of the fungus. Cystamine delayed protopla st regeneration and inhibited the yeast-to-mycelium transition and the incorporation of proteins into the cell wall. The incorporation of co valently bound high-molecular-weight proteins into the wall was sensit ive to cystamine. Proteic epitopes recognized by two monoclonal antibo dies, one of which is specific for the mycelial walls of the fungus, w ere also sensitive to cystamine. These data suggest that transglutamin ase may be involved in the formation of covalent bonds between differe nt cell wall proteins during the final assembly of the mature cell wal l.