The immediate precursor of mevalonic acid is
High-Yield Explanation
Beta-hydroxy beta-methyl glutaryl CoA (HMG CoA). The reduction of HMG CoA to mevalonate is catalysed by HMG CoA reductase. It is a microsomal (endoplasmic reticulum) enzyme.Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 148