Chemistry Reference
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(c)
(d)
Figure 9.1
(
Continued
)
pathway for formation of dopamine from tyrosine is not clear. The second
substrate,
p
-hydroxyphenylacetaldehyde,
is generated by transamination and
decarboxylation of tyrosine (10, 11).
Condensation of dopamine and
p
-hydroxyphenylacetaldehyde is catalyzed by
norcoclaurine synthase to form (S)-norcoclaurine (Fig. 9.1b). Two norcoclau-
rine synthases with completely unrelated sequences were cloned (
Thalictrum
flavum
and
C. japonica
) and heterologously expressed in
E. coli
(12-14). One
