3. Building blocks of nucleic acids (DNA and RNA).
Involved in energy storage, muscle contraction,
active transport, maintenance of ion gradients.
Activated intermediates in biosynthesis (e.g. UDP-
glucose, S-adenosylmethionine).
Components of coenzymes (NAD+, NADP+, FAD
FMN, and CoA)
Metabolic regulators:
a. Second messengers (cAMP, cGMP)
b. Phosphate donors in signal transduction (ATP)
c. Regulation of some enzymes via adenylation and
uridylylation
8. GTP is the energy source for AMP synthesis,
and ATP is the energy source for GMP.
AMP is made by N addition from aspartate (in
the familiar way).
GMP is made by oxidation at C-2, followed by
replacement of the O by N (from Gln).
Last step of GMP synthesis is identical to the
first two steps of IMP synthesis.
9.
10. Purines and pyrimidines in excess of cellular
requirements can be degraded.
Humans cannot degrade purines beyond uric
acid because of lack of uricase enzyme.
Excess AMP is deaminated to IMP by the
action of a specific deaminase.
IMP is then hydrolyzed by 5’-nucleotidase to
form inosine.
Inosine and guanine are oxidized to urate.
