Biology Reference
In-Depth Information
H
R1
R3
Phenyl
alanine
HO
PAL
R2
R1:
H
OH
OMe
OMe
OMe
Cinnamate
R2:
H
H
H
OMe
OH
Aromatic ring modifications
R3:
C4H
F5H
O
OH
C3H
COMT
COMT
4-
Coumarate
5-Hydroxy-
ferulate
Caffeate
Ferulate
Sinapate
C
4CL
4CL
4CL
4CL
4CL
CCOMT
O
S-CoA
4-
Coumaroyl-
CoA
5-Hydroxy-
feruloyl-
CoA
CCOMT
Caffeoyl-
CoA
Feruloyl-
CoA
Sinapoyl-
CoA
C
HCT
HCT
ALDH
ALDH
C3'H
O
O-shik
4-
Coumaroyl-
shikimate
CCR
CCR
CCR
CCR
CCR
Caffeoyl-
shikimate
C
SmF5H
O
5-Hydroxy-
conifer-
aldehyde
COMT
4-Coumar
aldehyde
Caffeyl-
aldehyde
Conifer
aldehyde
Sinap
aldehyde
C
H
COMT
F5H
CAD
CAD
CAD
CAD
OH
SmF5H
F5H
COMT
5-Hydroxy-
coniferyl
alcohol
COMT
4-Coumaryl
alcohol
Caffeyl
alcohol
Coniferyl
alcohol
Sinapyl
alcohol
CH
2
H-lignin
G-lignin
S-lignin
Fig. 1. The phenylpropanoid grid. The basic structure of phenylpropanoids is
shown on top. Head group modifications are shown top to bottom, and aromatic ring
modifications are shown left to right. The individual residues (R1-R3 in the general
structure) are shown at each level. Reactions that have been characterized to occur
with kinetic properties rendering a physiological function likely are drawn in black (or
dark grey if they occur only in the lycopod Selaginella moellendorffii [Sm]), those
occurring with low efficiency are shown in light grey. The currently accepted path
through the grid to H-, G-, and S-lignin are highlighted by bolder arrows. The
enzymes catalysing each step are given, for abbreviations see text.
Especially in woody tissues flow through the phenylpropanoid pathway
into lignin is massive and lignin is the primary carbon sink derived from the
shikimate pathway that produces the aromatic amino acids including Phe.
However, Phe itself and the vast array of other metabolites derived from it
also serve vital biological functions, for example, as protein building blocks,
