new stuff for exam 3 Flashcards
Ribonucleotide reductase
2 control sites: activity site (turns on or off) and specificity site (controls which substrate binds)
when is ribonucleotide reductase turned on
high ATP
ATP binds to activity site to turn ON
what happens when dATP concentration rises?
dATP displaces ATP at activity site and turns enzyme OFF
dNDP to dNTP
ATP + dNTP to ADP + dNTP
E: nucleoside diphosphate kinase
synthesizing thymine
dUMP to dTMP
E: thymidylate synthase
regulation of dNTP synthesis occurs when
right before and during S phase of cell cycle
regulation of dNTP synthesis
1) increases general purine and pyrimidine synthesis by increasing levels of synthetic enzymes
2) express ribonucleotide reductase
3) express thymidylate synthase
4) express TMP kinase
Thymidylate synthase
dUMP is substrate
1 carbon carrier is 5,10 methylene THF
what is leftover after nucleotides are deaminated?
ribose
nucleotide salvage
we can add bases back to ribose
PRPP + hypoxanthine to IMP
purine degradation
AMP or IMP to hypoxanthine
creates uric acid which must be excreted
pyrimidine degradation
open rings
products are small molecules that are water soluble and can be degraded
glutamine analogs
inhibit glutamate, inhibit lots of enzymes
sometimes a cancer treatment
build up of dATP leads to
inability to make sufficient deoxyribonucleotides for DNA replication
where is cholesterol stored in the liver?
lipid droplets
stored by ACAT
well-fed state hormones
insulin: reports on blood glucose
leptin: senses stored energy as fat
leptin
senses stored energy as fat in adipocytes
leptin and gene expression
JAK kinases phosphorylate STATS which dimerize and move to nucleus to alter gene transcription
sirtuin
a deacetylase that targets histones
responds to energy change
if there isn’t enough energy around to make cholesterol,
AMPK phosphorylates HMG-CoA reductase to turn OFF the pathway
AMPK functions
senses AMP and ATP binding
AMP activates AMPK
ATP inhibits AMPK
