ACS2, a Saccharomyces Cerevisiae Gene Encoding Acetyl-Coenzyme A Synthetase, Essential for Growth on Glucose

Abstract

In Saccharomyces cerevisiae, the conversion of pyruvate to acetyl‐coenzyme A may proceed directly via the pyruvate dehydrogenase complex (PDH) or indirectly via the so‐called PDH bypass, which requires the sequential action of pyruvate decarboxylase, acetaldehyde dehydrogenase and acetyl‐coenzyme A synthetase. The relative contribution of both pathways to the rate of acetyl‐coenzyme A synthesis varies in an unknown way with cultural conditions. To determine the possible role of acetyl‐coenzyme A synthetase in this central part of metabolism, we have analyzed the genes encoding this enzyme. Disruption of the recently cloned ACS1 gene [De Virgilio, C., Burckert, N., Barth, G., Neuhaus, J., Boiler, T. & Wiemken, A. (1992) Yeast 8, 1043–1051] did not cause an apparent phenotype, except for a prolonged lag‐phase during growth on glucose or C2 compounds such as acetate and ethanol. In fact, a product from a different gene is responsible for acetyl‐coenzyme A formation in the acs1 mutant. We cloned a second gene encoding acetyl‐coenzyme A synthetase, which we called ACS2. Inactivation of this gene caused inability to grow on media containing glucose, but not on media with acetate or ethanol as the sole carbon source. This indicates that ACS2 is essential for growth on glucose in batch cultures. The acs1‐acs2 double mutant was not viable. The role of both genes in glucose metabolism and acetate or ethanol metabolism is discussed.

Osmoadaptation of wine yeast (Saccharomyces cerevisiae) during Icewine fermentation leads to high levels of acetic acid

“…Respiratory growth and glucose limitation were used to induce ACS1 expression (van den Berg et al . ) while anaerobic growth conditions were used to induce ACS2 expression (van den Berg and Steensma ). Figure a illustrates that the design of the ASC1 probe was specific to differentiate between ASC1 and ASC2 , as the probe bound to the RNA from the Δ ACS2 strain but not to the RNA from the Δ ACS1 strain.…”

“…However, the isoenzyme encoded by ACS2 is required for fermentative growth on glucose (van den Berg and Steensma ). ACS2 was expressed in both fermentation conditions in the present study, but expressed at a much lower level up to day 4 of the Icewine fermentation.…”

“…The mitochondrial isoform encoded by ACS1 is reported to be present during respiratory growth and glucose repressed (van den Berg et al . ), while the cytosolic isoform ACS2 is required for growth on glucose under anaerobic conditions (van den Berg and Steensma ). Akamatsu et al .…”

Why are essential genes essential? - The essentiality of Saccharomyces genes

“…Another example is the Acetyl-CoA synthetase gene ACS2 , which is required for fermentative growth on glucose. Null mutant is inviable in YPD medium, but is capable of respiratory growth on non-fermentable carbon sources, such as ethanol 6. Therefore, the “optimal growth condition” for acs2 Δ, is non-fermentable carbon sources, rather than glucose.…”

The Saccharomyces cerevisiae acetyl-coenzyme A synthetase encoded by the ACS1 gene, but not the ACS2-encoded enzyme, is subject to glucose catabolite inactivation

“…In S. cerevisiae , the structural genes ACS1 and ACS2 each encode an active ACS isoenzyme [4, 5]. The ACS1 ‐encoded isoenzyme is only expressed during respiratory and respirofermentative growth, whereas the ACS2 product is also present under anaerobic conditions[6].…”