Structural studies on Pyruvate decarboxylase from Kluyveromyces lactis

During aerobic growth both respiration and fermentation may contribute to glucose catabolism in yeast. In Saccharomyces cerevisiae the respiratory and fermentative metabolism are tightly regulated and mutually exclusive. Glucose repression allows pyruvate to be almost completely consumed by pyruvate decarboxylase to yield acetaldehyde and carbon dioxide. In the majority of other yeast strains, including Kluyveromyces lactis, the respiratory metabolism of glucose predominates under aerobic conditions. The pathway is not glucose repressed or is repressed to a lesser extent [1]. Pyruvate decarboxylase catalyses the degradation of pyruvate, the end product of glycolysis, at this critical branching point between respiration and fermentation and should therefore be regulated in a different way in Kluyveromyces lactis and in Saccharomyces cerevisiae, respectively. Pyruvate decarboxylase from S. cerevisiae is functionally and structurally very well characterised [2]. In contrast, except for the detailed analysis of the substrate activation behaviour [3] hardly anything is known about pyruvate decarboxylase from K. lactis. Like all other yeast pyruvate decarboxylases, that from K. lactis is thiamine diphosphate dependent and the catalytically active form is the tetramer (molecular mass of subunit 61.7 kDa). Here, we present results of measurements of the dependence of scattering parameters on pH an