| Except where noted otherwise, data are given for|
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references
(E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP, HMBPP) or (E)-4-hydroxy-dimethylallyl pyrophosphate (HDMAPP) is an intermediate of the non-mevalonate pathway of isoprenoid biosynthesis. The enzyme HMB-PP synthase (GcpE, IspG) catalyzes the conversion of 2-C-methyl-D-erythritol 2,4-cyclopyrophosphate (MEcPP) into HMB-PP, and HMB-PP is then converted further to isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) by HMB-PP reductase (LytB, IspH).
HMB-PP is the physiological activator ("phosphoantigen") for human Vγ9/Vδ2 T cells, the major γδ T cell population in peripheral blood. With a bioactivity of 0.1 nM it is 10,000-10,000,000 more potent than any other natural compound, such as IPP or alkyl amines.
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- Eberl M, Hintz M, Reichenberg A, Kollas AK, Wiesner J, Jomaa H. Microbial isoprenoid biosynthesis and human γδ T cell activation. FEBS Lett. 2003;544:4–10. PMID 12782281