L-Arabinose transport and catabolism in yeast

Abstract

Two yeasts, Candida arabinofermentans PYCC 5603T and Pichia guilliermondii PYCC 3012, which show rapid growth on l-arabinose and very high rates of l-arabinose uptake on screening, were selected for characterization of l-arabinose transport and the first steps of intracellular l-arabinose metabolism. The kinetics of l-arabinose uptake revealed at least two transport systems with distinct substrate affinities, specificities, functional mechanisms and regulatory properties. The l-arabinose catabolic pathway proposed for filamentous fungi also seems to operate in the yeasts studied. The kinetic parameters of the initial l-arabinose-metabolizing enzymes were determined. Reductases were found to be mostly NADPH-dependent, whereas NAD was the preferred cofactor of dehydrogenases. The differences found between the two yeasts agree with the higher efficiency of l-arabinose metabolism in C. arabinofermentans. This is the first full account of the initial steps of l-arabinose catabolism in yeast including the biochemical characterization of a specific l-arabinose transporter. © 2007 The Authors.