Cytochrome P-450-catalysed monoterpenoid oxidation in catmint (Nepeta racemosa) and avocado (Persea americana); evidence for related enzymes with different activities.
A cytochrome P-450 present in ripening avocado (Persea americana) fruit mesocarp (CYP71A1) had previously been shown to metabolize the monoterpenoids nerol and geraniol (Hallahan et al. (1992) Plant Physiol. 98, 1290-1297). Using DNA encoding CYP71A1 as a hybridization probe, we have shown by Southern analysis that a related gene is present in the catmint, Nepeta racemosa. RNA blot analysis, together with Western analysis of catmint leaf polypeptides using avocado cyt P-450 antiserum, showed that a closely related gene is expressed in catmint leaves. Cytochrome P-450 in catmint microsomes catalysed the specific hydroxylation of nerol and geraniol at C-10, whereas avocado CYP71A1, in either avocado microsomes or heterologously expressed in yeast, catalysed 2,3- or 6,7-epoxidation of these substrates. These results suggest that orthologous genes of the CYP71 family are expressed in these two plant species, but catalyse dissimilar reactions with monoterpenoid substrates.
Hallahan
D L
DL
Biochemistry and Physiology Department, AFRC Institute of Arable Crops Research, Harpenden, Herts, UK.
Lau
S M
SM
Harder
P A
PA
Smiley
D W
DW
Dawson
G W
GW
Pickett
J A
JA
Christoffersen
R E
RE
O'Keefe
D P
DP
D000080462:Acyclic Monoterpenes; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D010084:Oxidation-Reduction; D010944:Plants / Q000201:enzymology / Q000235:genetics*; D013729:Terpenes / Q000378:metabolism*
D000080462:Acyclic Monoterpenes; D013729:Terpenes; D003577:Cytochrome P-450 Enzyme System; C007836:geraniol