Disease cycle of potato late blight - MSpace at the University of ...

from HMG CoA by a reaction catalyzed by the enzyme 3-hydroxy-3-methylglutaryl-CoA
reductase (HMGR). This enzyme is encoded by a small family of genes with different
pattern of expression, ranging from constitutive to tissue-specific induction. After two
remaining consecutive steps IPP is released and isopentenyl diphosphate (DMAPP) is
formed by the isomerization of IPP (Rodriguez-Concepcion and Boronat 2002;
Eisenreich et al. 2004; Phillips et al. 2008) (Fig. 1.3).
The DOXP-MEP pathway, also called the non-mevalonate route, consists of eight
reactions catalyzed by nine enzymes, seven of which are characterized structurally
(Hunter et al. 2003). Briefly, 1-deoxy-D-xylulose 5-phosphate (DXP) obtained by
condensation of pyruvate and D-glyceraldehyde 3-phosphate (GAP) in a reaction
catalyzed by the enzyme 1-deoxy-D-xylulose 5-phosphate synthase (DXS) undergoes a
reorganization associated with a reduction step. The next step of the DOXP-MEP
pathway is the conversion and reduction of DXP to 2C-methyl-D-erythritol 4-phosphate
(MEP) by the enzyme 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR). MEP is
subsequently transformed to IPP and DMAPP by five-independent steps by the action of
the enzymes 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase (MCT), 4-
(cytidine 50-diphospho)-2-Cmethyl-D-erythritol kinase (CMK) and 2-C-methyl-D-
erythritol 2,4-cyclodiphosphate synthase (MDS). In two final steps catalyzed by (E)-4-
hydroxy-3-methylbut-2-enyl diphosphate synthase (HDS) and reductase (HDR), IPP and
DMAPP are formed (Rodriguez-Concepcion and Boronat 2002; Eisenreich et al. 2004;
Phillips et al. 2008) (Fig. 1.4).
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