Appl. Environ. Microbiol., Sep 1997, 3341-3344, Vol 63, No. 9
KA Donald, RY Hampton and IB Fritz
The enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase
(HMG-R) is the major rate-limiting enzyme of the mevalonate pathway in many
organisms, including yeasts. In the yeast Saccharomyces cerevisiae, there
are two isoenzymes of HMG-R (Hmg1p and Hmg2p). Both consist of an anchoring
transmembrane domain and a catalytic domain. We have removed the known
controlling features of HMG-R by overproducing the catalytic domain of
Hmg1p. This overproduction leads to an enhancement of squalene production,
implying that HMG-R has been deregulated. The enhancement is apparent under
semianaerobic and aerobic conditions. Despite the increase in squalene
production, the amount of ergosterol produced by the HMG-R-overproducing
yeast was not increased. This result suggests the presence of another
regulatory step between squalene and ergosterol formation. Squalene levels
generated by cells overproducing the catalytic domain of HMG-R were
estimated to be up to 10 times those produced by wild-type cells. The
enhancement in squalene production coincided with a reduction in growth
rate. This reduction may be a direct consequence of the buildup of high
concentrations of squalene and presqualene intermediates of the pathway.
Copyright © 1997, American Society for Microbiology
Effects of overproduction of the catalytic domain of 3-hydroxy-3- methylglutaryl coenzyme A reductase on squalene synthesis in Saccharomyces cerevisiae
Department of Cellular Physiology, Babraham Institute, Cambridge, United Kingdom. allen.donald@bbsrc.ac.uk
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