Performs the first committed step in the biosynthesis of isoprene-containing compounds such as sterols and terpenoids (PubMed:10344201, PubMed:26216978). Is specific for (R)-5-diphosphomevalonate (MVAPP). The catalytic efficiency with (R)-5-phosphomevalonate (MVAP) as substrate is 10000-fold lower than for MVAPP (PubMed:26216978). Can complement a yeast mutant defective in MVD activity (PubMed:10344201). (R)-5-diphosphomevalonate + ATP = ADP + CO2 + isopentenyl diphosphate + phosphate kcat is 2.0 sec(-1) with (R)-5-diphosphomevalonate as substrate (PubMed:24327557). kcat is 3.2 sec(-1) with (R)-5-diphosphomevalonate as substrate (PubMed:26216978). kcat is 0.033 sec(-1) with (R)-5-phosphomevalonate as substrate (PubMed:26216978). Isoprenoid biosynthesis; isopentenyl diphosphate biosynthesis via mevalonate pathway; isopentenyl diphosphate from (R)-mevalonate: step 3/3. Homodimer. Decreased contents of campesterol and sitosterol (by 50% and 30%, respectively, compared with wild type). Decreased emissions of beta-caryophyllene (by 35% compared with wild-type). Belongs to the diphosphomevalonate decarboxylase family. Truncated N-terminus.