|
Examples of Tetrahydrofolate-Dependent
Reactions |
A. N5-Methyl-THF (Fig. 20-32, Rxn 4)
B. N5,N10-Methylene-THF (Fig. 20-14, Rxn 4)
C. N5-Formimino-THF (Fig. 20-17, Rxn 11)
|
S-ADENOSYLMETHIONINE
– Another Important Methyl Donor |
Fig. 20-18 Reaction # 1
|
Examples of S-Adenosylmethionine-Dependent
Reactions |
A.
B.
|
BIOSYNTHESIS OF AAs |
MAMMALS
·
Essential AAs: Those AAs which
cannot be synthesized (or cannot be synthesized in sufficient quantity) by mammals
and, hence, must be obtained from diets.
·
See Table 20-3
for the 10 essential AAs for human.
·
Nonessential AAs: Those AAs which can
be synthesized in sufficient quantities by mammals from common intermediates.
PLANTS
·
Can synthesize
all the AAs required for protein synthesis.
·
Can utilize NH3, NO2–,
NO3–, and (for legumes) N2
as N source.
MICROORGANISMS
·
Vary from one
extreme to another.
KNOWN PRECURSOR-PRODUCT RELATIONSHIPS
(Primarily
based on bacterial systems.)
SUMMARY
