Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Fri, 30 Nov 2018 17:36:40 Journal of General Microbiology (1987), 133, 609-61 7. Printed in Great Britain 609 Exo-l,3-P-glucanase Activity in Candida albicans: Effect of the Yeast- to-mycelium Transition By MARiA MOLINA, ROSA CENAMOR AND CESAR NOMBELA* Departamen to de Microbiologia, Facultad de Farmacia, Universidad Complutense, 28040- Madrid, Spa in (Received I August 1986; revised 3 November 1986) Yeast cells of Candida albicans 1001 produced glucan-hydrolysing activity, most of which was due to an exo-l,3-P-glucanase. The enzyme was periplasmically located; it could be found in culture medium samples, and was secreted by protoplasts when cultured under regeneration conditions. In contrast to most yeast exoglucanases, this enzyme was practically inactive against p-nitrophenyl-P-D-glucoside, hydrolysis of this substrate being carried out by a P-glucosidase located inside the cytoplasmic membrane and not secreted to the external medium. Supernatant fluids from cell-free extracts reached their maximum glucanase level after several days at 0 "C, suggesting that the active enzyme was formed from an inactive precursor. Glucanase activity substantially decreased and sometimes disappeared from the cells when the yeast-to-mycelium transition was induced, but a significant (though lesser) reduction was also observed in yeast cells incubated in the same medium under conditions (temperature, cell concentration) that did not lead to formation of hyphae. It is suggested that C. albicans exo-1,3-P-glucanasemay not be necessary for mycelial growth. INTRODUCTION Candida albicans can grow as an oval-shaped, unicellular yeast or as a filamentous fungus, when appropriate changes in the environment determine that yeast cells (blastospores) give rise to hyphae. Whereas much information exists regarding environmental factors that control the morphological transition in this yeast (Lee et al., 1975; Manning & Mitchell, 1980; Shepherd et al., 1980; Odds, 1983, data concerning biochemical changes involved in the differentiation process are scarce (Chiew et al., 1980; Niimi et al., 1980; Sullivan et al., 1983) and approaches towards an understanding of the genetic basis of dimorphism in C. albicans have only begun (Pomts et al., 1985; Hubbard et al., 1986). As in the case of many other fungi, glucan, with either 1,3-P- or 1,6-P-linkages,represents the main structural component of the cell wall of C. albicans (Sullivan et al., 1983; Gopal et al., 1984), and this species produces glucanases. C. albicans thus provides a model system for studying the properties of these cell-wall-degrading enzymes and their role in growth and morphogenesis. There are few reports on glucanases produced by C. albicans and the results are conflicting in some respects. Barrett-Bee et al. (1982) studied variations in glucanase levels during the growth cycle of C. albicans. Notario (1982)detected an endo-P-glucanase and an exo-/)-glucanase(which also had P-glucosidase activity as it hydrolysed the synthetic derivative p-nitrophenyl-P-D- glucoside) in cell-free extracts, culture fluids and cell wall autolysates. On the other hand, Ram et al. (1984), without making a very thorough fractionation of cell-free extracts, presented evidence suggesting that C. albicans exo-/I-glucanase and P-glucosidase are different enzymes. In this report, we examine some aspects of the production, localization and activation of glucanase in C. albicans and changes in enzyme levels that occur as a result of the morphological transition. Abbreviation : pNPG, pnitrophenyl /?-D-glucoside. 0001-3625 0 1987 SGM