exam 1 Flashcards
pasteur effect
low [glucose] and high [o2] repress fermentation and induce TCA and oxidative phosphorylation
Transcriptional activators on TCA, ETC gene promoters
regulate synthesis to control concentration of enzyme
Transcriptional repressors on fermentation gene promoters
regulate synthesis to control concentration of enzyme
PTMs that increase their activity of the enzymes of TCA
regulate activity of enzymes
Crabtree effect
high glucose concentrations
(regardless of O2 concentration) repress oxidative phosphorylation and induce fermentation
Carbon catabolite repression
Expression of genes for the use of alternate carbon sources (other sugars, fats, methanol, etc) is repressed by the presence of significant level of glucose (high enough levels)
extension of Crabtree, common regulatory mechanism for many industrial microbes
Peroxisomes (P)
needed for metabolism of methanol (MeOH) and catalase expression
Can you get catalase production on glucose?
no
glucose represses transcription of catalase gene —> little catalase protein made since little catalase mRNA is made
repressor on catalase promoter
grow methanol (MeOH) only
peroxisomes + catalase
grow on only glucose
no catalase
grow on methanol (MeOH) + glucose
no catalase (bc of repressors)
catalase activity is activated by
PTMS in peroxisomes
Peroxisome
organelle containing
100’s of proteins that are mainly
repressed by carbon catabolite
crabtree effects mechanisms
• repressors on TCA/ETC gene promoters
• activators on Fermentation gene promoters
• PTM (post translational modifications ie. phosphorylation) on Fermentation enzymes to activate them
normal catalase production
catalase mRNA is translated in
cytoplasm, signal sequence on protein for import into peroxisome
result of carbon catabolite repression
Catalase is unstable in cytoplasm, yeast cell degrades it if it is loitering in cytoplasm if not imported efficiently into peroxisome
Imagine get catalase mRNA from strong constitutive promoter in glucose
• Catalase mRNA made in glucose conditions, translated but since there are no peroxisomes to
“shelter” it, it gets __________.
degraded
Can’t get active catalase made in
glucose-grown yeast cells
why secondary metabolites only made after trophophase/primary phase is over?
lots of regulatory mechanisms
where are the building blocks of secondary metabolites made?
made during making of primary metabolites
hitch in making secondary metabolite
HITCH: Dependence on primary
metabolism since many secondary
metabolites derived from substrates
which are primary metabolites
Regulation of secondary metabolites affected by
Presence of nonribosomal peptide
synthetases — enzymes that
polymerize peptides (branched and
cyclic) without ribosomes or mRNA (think ice cube tray)
Nonribosomal peptide synthetases
made only at end of primary metabolism for secondary metabolism but use amino acids made mainly during trophophase
why cyclosporin (2ndary metabolism, immunosuppressant
peptide) made in certain fungus made?
surpress insect immune system when attacking it, hurt other fungi