Catalytic properties of recombinant 3-hydroxy-3-methylglutaryl coenzyme A synthase-1 from Blattella germanica.

Blattella germanica is the first organism in which two cytosolic HMG-CoA synthase genes have been described: HMGS-1 (Martínez-González et al., 1993b) and HMGS-2 (Buesa et al., 1994). The HMGS-1 gene showed special features, which led us to characterize the kinetic properties of the enzyme it encodes. Here we report the expression of recombinant HMGS-1, the protocol of enzyme purification, and the measurement of kinetic parameters. The K(m) for acetyl-CoA is 15.2 microM and the Ki for the other substrate, acetoacetyl-CoA, is 1.26 microM, both similar to that of yeast, ox, and chicken liver enzymes; the Vmax of HMGS-1 measured in this paper is 66 mU, which is the lowest Vmax of the HMG-CoA synthases reported to date.

Coordinated expression and activity of 3-hydroxy-3-methylglutaryl coenzyme A synthase and reductase in the fat body of Blattella germanica (L.) during vitellogenesis.

Levels of mRNA for the two 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthases, (HMG-S1 and HMG-S2), and for HMG-CoA reductase (HMG-R) of Blattella germanica were analyzed in the fat body during the first gonadotrophic cycle. HMG-S2 and HMG-R showed the highest mRNA levels on day 0 and decreased thereafter, whereas HMG-S1, showed faint expression. Western blot using specific antibodies for HMG-S1 and HMG-S2 showed no detectable levels for HMG-S1 but a clear pattern for HMG-S2. Both results point to a very limited role for HMG-CoA synthase-1 in B. germanica fat body that the functional enzyme in this organ is HMG-CoA synthase-2. HMG-CoA reductase and synthase proteins shared a cyclic pattern (maximum levels at day 4 and minimum levels on days 0 and 8), which was coincident with the pattern of activity. The delay between gene transcription and protein synthesis suggests a finely regulated translation mechanism. Moreover, the pattern of mevalonate synthesis parallels that of vitellogenin production, suggesting a coordinate mechanism between the mevalonate pathway and the production of vitellogenin.