A vacuolar class III peroxidase and the metabolism of anticancer indole alkaloids in Catharanthus roseus: Can peroxidases, secondary metabolites and arabinogalactan proteins be partners in microcompartmentation of cellular reactions?
Plants possess a unique metabolic diversity commonly designated as secondary metabolism, of which the anticancer alkaloids from Catharanthus roseus are among the most studied. Recently, in a classical function-to-protein-to-gene approach, we have characterized the main class III peroxidase (Prx) expressed in C. roseus leaves, CrPrx1, implicated in a key biosynthetic step of the anticancer alkaloids. We have shown the vacuolar sorting determination of CrPrx1 using GFP fusions and we have obtained further evidence supporting the role of this enzyme in alkaloid biosynthesis, indicating the potential of CrPrx1 as a molecular tool for the manipulation of alkaloid metabolism. Here, we discuss how plant cells may regulate Prx reactions. In fact, Prxs form a large multigenic family whose members accept a broad range of substrates and, in their two subcellular localizations, the cell wall and the vacuole, Prxs co-locate with a large variety of secondary metabolites which can be accepted as substrates. How then, are Prx reactions regulated? Localization data obtained in our lab suggest that arabinogalactan proteins (AGPs) and Prxs may be associated in membrane microdomains, evocative of lipid rafts. Whether plasma membrane and/or tonoplast microcompartmentation involve AGPs and Prxs and whether this enables metabolic channeling determining Prx substrate selection are challenging questions ahead.
Sottomayor
Mariana
M
IBMC-Instituto de Biologia Molecular e Celular; Universidade do Porto; Porto Portugal.
Duarte
Patrícia
P
Figueiredo
Raquel
R
Ros Barceló
Alfonso
A
Plant Physiol. 2005 Jan;137(1):104-16
15618420
J Cell Biol. 1989 May;108(5):1967-77
2469683
J Biol Chem. 2004 Aug 27;279(35):36277-86
15190066
Annu Rev Plant Biol. 2007;58:137-61
17201686
Protoplasma. 2003 Sep;222(1-2):97-105
14513315
Plant Cell. 2004 Dec;16(12):3285-303
15539469
Planta. 1984 Sep;162(3):250-60
24253097
FEBS Lett. 1998 May 29;428(3):299-303
9654153
Plant Physiol. 2008 Feb;146(2):403-17
18065566
Plant Physiol. 2007 May;144(1):402-18
17337521