Mevalonate-5-phosphotransferase

When mevalonate, written below as the anion of (iJ)-mevalonic add (Chapter 6, Section C, I and Chapter 11), is acted upon by the enzyme mevalonate-5-phosphotransferase, a phosphate unit is transferred from adenosine triphosphate (ATP) to the primary alcohol of mevalonate. Adenosine diphosphate (ADP) and phosphomevalonate are produced. Although enzyme mediated, this process may be viewed as the reaction of an activated derivative of phosphoric acid (an anhydride ) reacting with an alcohol to produce an ester of phosphoric acid [H3PO4 or 0=P(0H)3]. 

MVA is phosphorylated in two steps to the mono- and the diphosphate (MVAP and MVAPP), by the specific ATP-dependent enzymes MVA kinase (ATP-mevalonate-phosphotransferase, EC 2.7.1.36) and MVAP kinase (EC 2.7.4.2), respectively. MVAPP is converted into IPP by a decarboxylase (EC 4.1.1.33). The kinases and the decarboxylase have not yet been given as much attention as HMG-CoA reductase, and have only been characterized in a few plant species. Recently, MVA kinase was partially purified from C. roseus suspension cultures. The enzyme proved to be unstable and was present only at low activity levels (90). 

Figure 2.11. Lipid synthesis. GDP = glycerol-3-phosphate dehydrogenase. PP = phosphat-idate phosphatase. CPT=choline phosphotransferase. BPT= ethanolamine phosphotransferase. AC = acetyl CoA carboxylase. HAD 3-hydroxyacyl-CoA dehydrogenase. CCPT = cemmide choline phosphotransferase. HMGR = hydroxymethyl utaryl-CoA reductase. MK = mevalonate kinase. IPPI = isopentenyl pyrophosphate isomerase...

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