It is a precursor to many natural products, especially
lignols, precursors to the woody mass that comprise many plants. Of the myriad occurrences,
p-coumaric acid can be found in
Gnetum cleistostachyum.
In food p-Coumaric acid can be found in a wide variety of edible plants and fungi such as
peanuts,
navy beans,
tomatoes,
carrots,
basil and
garlic. It is found in
wine and
vinegar. It is also found in
barley grain.
p-Coumaric acid from
pollen is a constituent of
honey.
Derivatives p-Coumaric acid glucoside can also be found in commercial
breads containing
flaxseed. Diesters of
p-coumaric acid can be found in
carnauba wax.
Biosynthesis It is biosynthesized from
cinnamic acid by the action of the
P450-dependent enzyme
4-cinnamic acid hydroxylase (C4H). : \begin{matrix}{}\\\xrightarrow\mathrm{C4H}\\{}\end{matrix} It is also produced from L-
tyrosine by the action of
tyrosine ammonia lyase (TAL). : \xrightarrow\mathrm{TAL} + NH3 + H+
Biosynthetic building block p-Coumaric acid is the precursor of
4-ethylphenol produced by the
yeast Brettanomyces in wine. The enzyme
cinnamate decarboxylase catalyzes the conversion of
p-coumaric acid into
4-vinylphenol.
Vinyl phenol reductase then catalyzes the reduction of 4-vinylphenol to 4-ethylphenol. Coumaric acid is sometimes added to
microbiological media, enabling the positive identification of
Brettanomyces by smell. :
cis-p-Coumarate glucosyltransferase is an enzyme that uses
uridine diphosphate glucose and
cis-
p-coumarate to produce
4′-O-β-D-glucosyl-cis-p-coumarate and
uridine diphosphate (UDP). This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases.
Phloretic acid, found in the
rumen of
sheep fed with dried grass, is produced by hydrogenation of the 2-propenoic side chain of
p-coumaric acid. The enzyme,
resveratrol synthase, also known as stilbene synthase, catalyzes the synthesis of
resveratrol ultimately from a tetraketide derived from
4-coumaroyl CoA.
p-Coumaric acid is a cofactor of
photoactive yellow proteins (PYP), a homologous group of proteins found in many eubacteria.
p-Coumaric acid is found as the base moiety of
caleicine, one of many
sesquiterpenes in
Calea ternifolia. == See also ==