Caracterización de la inulinasa e invertasa en Candida utilis

Abstract

lnvertase (E.C. 3.2.1.26) and inulinase (E.C. 3.2.1. 7) were analyzed in Candida utilis CECT 1061 to determine whether one single enzyme with both activities or two enzymes with different substrate specificities were present in this yeast. The synthesis of both fructofuranosidase activities was under control of catabolite repression by glucose and they were present in whole cell extracts as well as in the extracellular culture fluids. The cell-associated activities appear mostly located in the periplasmic space. The two activities exhíbited an identical optimum pH and similar profiles of thermal denaturation. In addition, a constan! ratio was found between the inulinase and the invertase activities in a variety of culture condítions when extracellular media or cell extracts were assayed. From the results obtained it was concluded that both activities reside in a same protein of molecular weight close to 450,000 dalton which shows a different affiníty for sucrose and inuline, Km values were 14 and 0,62mM. respectively.

La actividad invertasa (E.C. 3.2.1.26) e inulinasa (E,C. 3.2.1.7) se ha analizado en Candida utilis CECT 1061 para determinar si en esta levadura existe una única enzima con ambas actividades o dos enzimas diferentes con distinta especificidad de sustrato. La síntesis de ambas fructofuranosidasas parece regulada por represión catabólica por glucosa y ambas se presentan tanto en extractos celulares como extracelularmente. La actividad detectada en extractos celulares aparece fundamentalmente localizada a nivel periplásmico. Las dos actividades exhiben idéntico pH óptimo y similar resistencia a la desnaturalización por calor. Además, la relación de actividad inulinasa/actividad invertasa se mantiene constante en distintos medios de cultivo tanto en células como en el medio extracelular. Los resultados sugieren que ambas actividades se deben a una misma enzima de peso molecular próximo a 450.000 dalton que muestra diferente afinidad por sacarosa o inulina. Los valores Km fueron 14 y 0,62 mM, respectivamente.