both of which inhibit NT activity. Acid Trehalase The molecular weight of AT was found to be 218 kDa by gel filtration chromatography. AT is a glycoprotein. It has 86% carbohydrate content. It has been reported that the maturation of AT is a stepwise process beginning with a carbohydrate-free 41 kDa protein; this form is then core-glycosylated in the endoplasmic reticulum to form a 76 kDa glycol-protein. In Golgi bodies, the protein is further glycosylated yielding a 180 kDa form, which ultimately attains a maturity in vacuoles, where its molecular weight becomes around 220 kDa. The 41 kDa carbohydrate free protein moiety of the enzyme was obtained by Endoglycosidase H treatment of purified AT, resulted after sodium dodecyl sulfate gel electrophoresis27. AT exhibited an apparent Km for trehalose of about 4.7 mM at pH 4.5. The gene responsible for AT activity in S. cerevisiae is ATH1. Ath1p, i.e. AT, has been reported to be necessary for S. cerevisiae to utilize extracellular trehalose as carbon source16. ATH1 deletion mutant of the yeast could not grow in the medium with trehalose as the carbon source. Researchers have suggested that AT moves from its site of synthesis to the periplasmic space, where it binds exogenous trehalose to internalize it and hydrolyze it in the vacuoles. Recently it has been shown that more than 90% of AT activity in S. cerevisiae is extracellular and the hydrolysis of trehalose into glucose takes place at the periplasmic space. Previously, a highly glycosylated protein, gp37, which is the product of YGP1 gene, was reported to be co-purified with AT activity. Invertase activity was also reported to be co-purified with AT activity. The physical association of AT with these two proteins was thought to suffice for the AT to be secreted by invertase and gp37 secretion pathways in absence of any known secretion signal for Ath1p. In a Candida utils strain, one regulatory a one non-regulatory trehalase were also reported. These two enzymes were reported to be distinguishable by their molecular weight, behavior in ion-exchange chromatography and kinetic properties. The regulatory trehalase appeared to be a cytoplasmic enzyme and the nonregulatory enzyme was mostly detected in vacuoles. But, in a more recent report, a C. utils strain was demonstrated to lack any detectable AT activity but contain only NT activity. AT activity was not detectable in this strain, though the strain was shown to utilize extracellular trehalose as