Catabolite interconversion of glucose transport systems in the yeast Candida wickerhamii |
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| Affiliation: | 1. Department of Microbiology, University of Karachi, Karachi 75270, Pakistan;2. Department of Biosciences, Shaheed Zulfikar Ali Bhutto Institute of Science and Technology (SZABIST), Pakistan;3. Dr zafar H zaidi center for proteomic (formerly National Center for Proteomics) University of Karachi, Karachi 75270, Pakistan;4. Department of Chemistry, College of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia;5. Department of Chemistry, Turabah University College, Taif University, P.O. Box 11099, 12, Taif 21944, Saudi Arabia;1. Department of Studies in Microbiology, University of Mysore, Manasagangotri, Mysuru, 570 006, Karnataka, India;2. Department of Microbiology, Yuvaraja''s College (Autonomous), University of Mysore, Mysuru, 570 005, Karnataka, India;3. Department of Studies in Environmental Science, University of Mysore, Manasagangotri, Mysuru, 570 006, Karnataka, India;1. Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran;2. Department of Veterinary Microbiology and Immunology, College of Veterinary Sciences, UP Pandit Deen Dayal Upadhayay Pashu Chikitsa Vigyan Vishwavidyalay Evum Go-Anusandhan Sansthan, Mathura, Uttar Pradesh, India;3. Central University Laboratory, Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu, India;4. Department of Veterinary Microbiology, College of Veterinary Sciences and Animal Husbandry, R.K. Nagar, West Tripura, India;5. Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India |
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| Abstract: | Candida wickerhamii IGC 3244 growing in glucose medium transported glucose by facilitated diffusion (at 25°C and pH 5, the Ks value was 1.7 mM and the Vmax value was 1.6 mmol/h per g dry wt.), while cells grown under derepressed conditions produced a glucose proton symport (at 25°C and pH 5, the Ks value was 0.18 mM and the Vmax value was 1.8–1.9 mmol/h per g dry wt.). In each case, the Lineweaver-Burk plot of initial uptake rates was linear, indicating the presence of a single system. In buffer with 2% glucose, the symport suffered catabolite inactivation while the facilitated diffusion system emerged concomitantly in such a way that the combined Vmax remained nearly constant. During the conversion process, the Linewaver-Burk plots were biphasic, indicating the transitory co-existence of the two systems. A model is proposed that envisions the proton symport as composed of the facilitated diffusion system in association with (an)other transport protein(s), the latter being sensitive to carbon catabolite repression and inactivation. |
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