Introduction to Enzyme and Coenzyme Chemistry - E-Library Home

Enzymatic Transformations of Amino Acids 223
HO
N
N
H
N
Me
HO
O
H
H
NMe
O
N
H
H
O
nicotine
morphine
Figure 9.17 Alkaloid natural products.
strychnine
H 3 N
L-lysine
H
CO −
2
NH 3
+
lysine
decarboxylase
PLP
H 2 N
NH 2
FAD,O 2 or PMP
O
NH 2
N
H
N
H
H
N
H
N
CHO
hydrolysis
NH
NH
NH
NH 2
H
OH
CHO
oxidase
CHO
reduction
N
2 NADH
N
NH
O
Figure 9.18 Biosynthesis of lupinine.
symmetrical diamine. Oxidative deamination of one amino group, probably by
a Xavin-dependent oxidase, generates an amino-aldehyde. This condenses to
give a cyclic imine, which in turn isomerises to give a cyclic enamine. Reaction
of one equivalent of the enamine with another equivalent of the imine forms a
carbon–carbon bond between the two lysine-derived species. Hydrolysis of the
resulting imine, followed by formation of a second imine linkage, leads to the
natural product lupinine as shown in Figure 9.18.