Mevalonate 5-diphosphate decarboxylase Mevalonic acid

This enzyme [EC 4.1.1.33] (also known as mevalonic acid 5-pyrophosphate anhydrodecarboxylase, mevalonate-5-diphosphate decarboxylase, and diphosphomevalonate decarboxylase) catalyzes the reaction of ATP with (R)-5-diphosphomevalonate to produce ADP, orthophosphate, isopentenyl diphosphate, and carbon dioxide. 

Fig. 11 Natural rubber is produced from a side branch of the ubiquitous isoprenoid pathway, with 3-hydroxy-methyl-glutaryl-CoA (HMG-CoA) as the key intermediate derived from acetyl-CoA by the general mevalonic-acid pathway. Mevalonate diphosphate decarboxylase (MPP-D) produces IPP, which is isomeiized to DMAPP by IPP isomerase (IPI). IPP is then condensed in several steps with DMAPP to produce GPP, FPP and GGPP by the action of a trani-prenyltransferase (TPT). The cA-l,4-polymeiization that yields natural rubber is catalyzed by cA-prenyltransferase (CPT), which uses the non-allylic IPP as substrate. Reprinted from [248], with permission from Elsevier...

The conversion of mevalonate (1) to isopentenyl pyrophosphate (IPP) (4) involves two consecutive phosphorylations at position 5 by successive action of mevalonate kinase (EC 2.7.4.2) and a decarboxylation and dehydration of the tertiary alcohol group by mevalonate 5-pyrophosphate decarboxylase (EC 4.1.1.33) (Fig. 18.4) (Crotean Johnson, 1985 Gershenzon and Croteau, 1990). One mole of ATP is required for each phosphorylation reaction. Mevalonate kinase converts mevalonic acid to (5/ )-phosphomevalonate (5). The second phosphorylation is catalyzed by phospho-mevalonate kinase. The subsequent decarboxylation and dehydration is mediated by the enzyme mevalonate diphosphate decarboxylase (di- or pyrophosphomevalonate decarboxylase EC 4,1.1.3.3) this enzyme requires Mg " or Mn + and ATP for activity (Beale and MacMillan, 1988 Harrison, 1988). All three of these enzymes are found in a number of plants. 

Then (Scheme 11.41) mevalonate [(l )-3,5-dihydroxy-3-methylpentanoic acid] is phosphorylated by the enzyme mevalonate kinase (EC 2.7.1.36) at the primary hydroxyl. The phosphate that is added is obtained (an addition-elimination reaction or a displacement reaction) from the terminal phosphate group of ATP forming ADP in turn. Another phosphorylation, again using ATP yields mevalonate diphosphate, this time by the enzyme phosphomevalonate kinase (EC 2.7.4.2) and then, after one more phosphorylation, this time on the tertiary hydroxyl, decarboxylation and dehydration co-occur, catalyzed by the enzyme mevalonate diphosphate decarboxylase (EC 4.1.1.43). The products are inorganic phosphate, carbon dioxide, and isopentenyl diphosphate (diphosphoric acid mono[3-methylbut-3-enyl] ester). Isopentenyl diphosphate isomerase (EC S.3.3.2) catalyzes the isomerization, via loss of the C2 pro-R hydrogen, between isopentenyl diphosphate and dimethylallyl diphosphate. 

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