Phytoecdysteroid C2-hydroxylase is microsomal in spinach, Spinacia oleracea L.
An enzyme involved in the biosynthesis of phytoecdysteroids, the C2-hydroxylase, has been investigated in spinach, Spinacia oleracea. This enzyme is microsomal and its K(m) has been determined using 2-deoxy-20-hydroxyecdysone as substrate (K(m)=3.72 microM). It is much more efficient with 2-deoxy-20-hydroxyecdysone than with 2-deoxyecdysone and, conversely, the C20-hydroxylase is more active on 2-deoxyecdysone than on ecdysone. These data support the conclusion that C20-hydroxylation precedes C2-hydroxylation. The C2-hydroxylase is inhibited by high concentrations of 20E. Substrate specificity and subcellular localization of C2-hydroxylase differ between plants and insects, and these data, as well as those previously reported on other biosynthetic steps, show the great difference between plant and insect ecdysteroid biosynthetic pathways and suggest an independent origin for the pathways in both kingdoms.
Bakrim
Ahmed
A
UPMC, Université Paris VI, Laboratoire de Biochimie Structurale et Fonctionnelle des Protéines, CNRS FRE 2852, Paris, France.
Guittard
Emilie
E
Maria
Annick
A
De Virville
Jacques Davy
JD
Lafont
René
R
Takvorian
Najat
N
D002851:Chromatography, High Pressure Liquid; D004440:Ecdysone / Q000378:metabolism; D004441:Ecdysterone / Q000096:biosynthesis*; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D018724:Spinacia oleracea / Q000737:chemistry / Q000201:enzymology*; D013379:Substrate Specificity
D010940:Plant Proteins; D004440:Ecdysone; D004441:Ecdysterone; D006899:Mixed Function Oxygenases