Biosynthesis of p-Hydroxybenzoate from p-Coumarate and p-Coumaroyl-Coenzyme A in Cell-Free Extracts of Lithospermum erythrorhizon Cell Cultures.
The enzymatic formation of p-hydroxybenzoate from p-coumarate in cell-free extracts of cell cultures of Lithospermum erythrorhizon Sieb. et Zucc. was investigated. p-Coumaroyl-coenzyme A (p-coumaroyl-CoA) is the activated intermediate in this biosynthetic reaction. It is formed by an ATP-, Mg2+ -, and CoA-dependent 4-hydroxycinnamate:CoA ligase reaction. p-Coumaroyl-CoA is oxidized and cleaved to p-hydroxybenzoyl-CoA and acetyl-CoA in a thioclastic reaction in which NAD is an essential cofactor. These CoA esters are rapidly hydrolyzed to acetate and p-hydroxybenzoate, probably by thioesterases. The enzymes involved in the formation of p-hydroxybenzoate are soluble. p-Hydroxybenzalde-hyde is not an intermediate in this conversion, and S-denosylmethionine and uridine-5[prime]-diphosphoglucose do not enhance formation of p-hydroxybenzoate in our system.
Loscher
R.
R
Institut fur Pharmazeutische Biologie, Albert-Ludwigs-Universitat Freiburg, Schanzlestrasse 1, 79104 Freiburg im Breisgan, Germany.
Heide
L.
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