HMG-CoA synthase is an enzyme which catalyzes the reaction where Acetyl-CoA condenses with acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA). This reaction occurs at a faster rate in patients with Diabetes Insipidus type I if left untreated.
Forms
There are two different forms of the enzyme; in humans the cytosolic form has only 60.6% amino acid identity with the mitochondrial form of the enzyme.
HMG-CoA synthase reaction
Cytosolic
The cytosolic enzymes has a key role in the production of cholesterol and other isoprenoids:
Mitochondrial
The mitochondrial form is used for the production of ketone bodies:
Regulation
The gene for the mitochondrial form of the enzyme has three sterol regulatory elements in the 5' flanking region [1]. These elements are responsible for decreased transcription of the message responsible for enzyme synthesis when dietary cholesterol is high in animals: the same is observed for 3-hydroxy-3-methylglutaryl-CoA and the low density lipoprotein receptor.
External links
References
- ^ Goldstein J.L., Brown M.S. (1990) Regulation of the mevalonate pathway. Nature 343, 425-430
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