enzymes + inhibition Flashcards
how many times can enzymes increase the Ror
1013 faster
what is a coenzyme
small organic AA that participates in enzyme catalysed reaction + stable to heat
what is a prosthetic group
coenzyme that covalently/firmly bound to enzyme –> not removed by dialysis
what is zymogen
inactive precursor of enzyme
what is a haloenzyme
protein WITH coenzyme pr ions needed for activity
what is a apoenzyme
protein WITHOUT coenzyme or ions needed for activity,
labile (easily altered) to heat
where are lysosomes commonly found
saliva
tears
tissue fluids
nasal mucus
what do lysosomes do
protects against sensitive bacteria –> causing lysis of bacteria + losing cell content
how does lysosome cause bacteria lysis
hydrolyses beta 1-4 bond in glycol chain between N-acetyl glucosamine (NAG) + N-acetyl muramic acid (NAM)
when do lysosomes work the fastest
near neutral pH
another name serine protease?
proteolytic enzymes
how and why proteolytic enzymes secreted in the body
secreted as zymogens (inactive form ) then activated by gut
bc they needed for digestion of proteins - but the can work in human body - so harmful
name 3 zymogen forms of serine protease
trypsinogen
chymotrypsinogen
pepsinogen
how do you activate pepsinogen
pepsinogen –> pepsin
gastric gland: chief cells produce pepsinogen + parietal cells produce HCl
pepsinogen –> pepsin by HCl
how you do activate trypsinogen
pancreatic zymogens –> trypsinogen –> trypsin
trypsinogen –> trypsin by Enterokinase in cell walls of cells in duodenum
trypsin activates more zymogen like chymotrypsinogen
how long is chymotrypsin and how is it held together
245 AA
5 disulphide bonds between different parts of structure + folds into 3D globular structure
how is chymotrypsinogen activated
trypsin cleaves/cuts bond between Arg15 + 16
Pi-chymotrypsin cuts at Leu13 + removes dipeptide
Pi-chymotrypsin cuts at Tyr146 + removes another dipeptide
A chain = 1-13 alpha Chymotrypsin
B chain = 16-146
C chain = 149-245
3 parts of chain held by disulphide bridge
where are the active sites that come together in chymotrypsin
Asp102
His57
Ser195
name 3 enzymes which are used to cut polypeptide chain
trypsin
Chymotrypsin
elastase
where does trypsin cut next to and what are its pocket properties
cuts next to = basic R groups
Lysine + Arginine
bottom of the pocket
where does chymotrypsin cut next to and what are its pocket properties
cuts next to = hydrophobic R groups
Tyrosine + Phenylalanine
hydrophobic pocket
where does elastase cut next to and what are its pocket properties
cuts next to - small R groups
Glycine, Alanine, Valine
small pocket so large R groups don’t fit
what is Michaelis - mention equation + what does it show
V (initial velocity) = Vmax (max velocity) / Km (substrate conc at half Vmax) + S (substrate conc)
what happens as the substrate conc increases
increases For
eventually active sites of enzymes become saturated, so Ror stays the same
when is the fastest rate of reaction
Vmax
what does Km mean
substrate conc at half Vmax
what does a small Km value mean
tight binding between enzyme + substrate
what happens as enzyme conc increases
increases Ror
eventually all substrate converted to product –> Ror decreases to 0
what happens as the temp increases
increases energy + more frequent collisions
but if at too high temp, active site change shape so Ror decreases quickly
what happens if pH moves away from optimum pH
Ror decreases suddenly
why are enzyme inhibitors important
gain info on enzyme active site shape + amino acid at active site
gain info on chemical mechanism of reaction/ regulation or control of pathway
what are diff types of enzyme inhibitors
reversible + irreversible
how does a irreversible inhibitor work
substance causes irreversible inactivation to enzyme
involves forming or breaking of covalent bonds in enzyme
give a example of irreversible inhibition
diisopropylphosphofluoridate permanently inactives serine protease by forming covalent bond with serine AA in active site
how does reversible inhibition work
substance binds to enzyme active site to inhibit but can be reversed
involves formation of non-covalent bonds
describe steps in how competitive inhibition works
inhibitor competes with substrate for same active site in enzyme
only binds to free enzymes
reduces amount of free enzymes available for substrate binding
Ror decreases
how are Vmax and Km affected in competitive inhibition
Vmax = doesn't change bc can be reversed using high conc of substrate Km = increases bc affinity between substrate + enzyme decreases
give a example of competitive inhibition
malonate comp inhibitor of succinate for succinate dehydrogenase
describe steps in how non-competitive inhibition works
inhibitor binds to another site on enzyme not active site
can bind to free enzyme + ESC
how are Vmax and Km affected in non-competitive inhibition
Vmax = decreases --> binding stops the reaction Km = stays same as substrate can still bind to enzyme, same affinity
give 2 examples of non-comp inhibition
AMP inhibits fructose 1,6 bisphosphate
Alanine inhibits pyruvate kinase as converts phosphoenol pyruvate to pyruvate –> alanine
describe steps in how uncompetitive inhibition works + how are Vmax and Km affected in uncompetitive inhibition
inhibitor binds only to ESC
Vmax = decreases inhibitor stops reaction
Km = decreases –> tighter binding between enzyme + substrate bc when inhibitor binds, substrate can’t move out
how may types of reversible inhibition ae there + name them
3
comp
non-comp
uncomp
what are the type of allosteric effctors
negative + positive
how do positive allosteric effectors work
increased Ror
binds to allosteric site + makes substrate bind more tightly to enzyme –> higher affinity
Vmax increases + Km decreases
how do negative allosteric effectors work
decrease Ror
binds to allosteric site + changes shape of active site so substrate can’t bind to it
Vmax decreases + Km increases
