Ae. Haack et Ne. Balke, ENHANCEMENT OF MICROSOMAL BENTAZON 6-HYDROXYLASE AND CINNAMIC ACID 4-HYDROXYLASE ACTIVITIES FROM GRAIN-SORGHUM SHOOTS, Pesticide biochemistry and physiology, 50(1), 1994, pp. 92-105
Microsomes isolated from excised shoots of grain sorghum (Sorghum bico
lor, (L.) Moench) seedlings arylhydroxylated bentazon herbicide and ci
nnamic acid to 6-hydroxybentazon and p-coumaric acid, respectively. Co
nstitutive, unprotected bentazon 6-hydroxylase (EC 1.14.13.) activity
was low but measurable, whereas, constitutive, unprotected cinnamic ac
id 4-hydroxylase (EC 1.14.13.11) activity was much greater and was eas
ily measurable. Inclusion of the isolation medium additives (i.e., pro
tectants) ascorbate (40 mM), P-mercaptoethanol (14 mM), and EDTA (10 m
M) increased bentazon 6-hydroxylase and cinnamic acid 4-hydroxylase ac
tivities to levels 11.6 and 1.7 times the control activities, respecti
vely. Naphthalic anhydride seed treatment induced bentazon 6-hydroxyla
se activity to a level 1.9 to 8.0 times the control activity, dependin
g on the sorghum variety, but did not significantly induce cinnamic ac
id 4-hydroxylase activity in any variety. Isolation medium additives a
nd naphthalic anhydride seed treatment independently enhanced bentazon
6-hydroxylase activity resulting in a combined increase in activity 2
1.3 times the control activity. Differential responses of bentazon 6-h
ydroxylase and cinnamic acid 4-hydroxylase to isolation medium additiv
es and naphthalic anhydride seed treatment suggest that bentazon and c
innamic acid are hydroxylated by different microsomal monooxygenases i
n sorghum. (C) 1994 Academic Press, Inc.