SUMMARY PARAGRAPH for GND1
In Saccharomyces cerevisiae, GND1 encodes the major isoform of phosphogluconate dehydrogenase, accounting for approximately 80% of activity, and GND2 encodes the minor isoform (1). Phosphogluconate dehydrogenase (EC:220.127.116.11) is a key enzyme in the cytosolic oxidative branch of the pentose phosphate pathway (5), and catalyzes the second oxidative reduction of NADP+ to NADPH (3, 6, 1). Phosphogluconate dehydrogenase is also important for protecting yeast from oxidative stress, since NADPH is an essential cofactor for the Glr1p glutathione reductase as well as the Trr1p and Trr2p thioredoxin reductases, which defend cells against oxidative damage (2).
Gnd1p is of industrial interest for the fermentation of xylose to ethanol because NADPH is used in fungi to reduce pentoses like xylose, the predominant sugar found in biomass, to sugar alcohols (3). gnd1 null mutants are viable and display increased sensitivity to furfural, which is a growth inhibitory byproduct of xylose utilization (7). gnd1 nulls also display no growth on D-glucono-delta-lactone and no induction of 6-phosphogluconolactonase (SOL3 & SOL4) in response to D-glucono-delta-lactone (1). gnd1-100 mutants display increased FLO11 expression, increased invasion into agar, enhanced polar budding, and hyperfilamentation, which may depend on a glucose repression mechanism because these phenotypes do not occur in gnd1-100 snf1 null double mutants (8, 6). GND1 is induced during growth on D-glucono-delta-lactone (1), and is repressed during growth on ethanol or lactic acid (9). GND1 may also be repressed in zwf1 null mutants because of an insufficient supply of the substrate 6-phosphogluconate (2).
Gnd1p displays similarity to Gnd2p, and the 6-phosphogluconate dehydrogenases of Candida parapsilosis, Cryptococcus neoformans, and human (10, 11).
Last updated: 2006-01-25