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36 Cards in this Set
- Front
- Back
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catalysis by approximation
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nucleoside monophosphate kinases (NMP kinases) catalyze transfer of phosphoryl group from NTP to NMP without catalyzing hydrolysis of NTP.
conformation of enzyme changes upon binding substrates, facilitating reaction and preventing water from hydrolyzing NTP. |
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covalent catalysis
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nucleophilic attack results in temporary covalent attachment between enzyme and substrate
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acid/base catalysis
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uses molecule (not water) that can accept or donate a proton
-histidine is common because side chain has pKa ~7 that can function as acid/base at physiological pH |
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in aspartate ammonia lyase, deprotonated serine sidechain performs nucleophilic attack on carbonyl carbon of substrate
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covalent catalysis
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substrates of chymotrypsin
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cleaves peptide bonds after aromatic or bulky hydrophobic side chains
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substrates of trypin
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cleaves peptide bonds after basic amino acid residues
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substrates of elastase
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cleaves peptide bonds after small uncharged side chains
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specificity pocket of trpysin
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shorter, negative asp residue
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specificity pocket of chymotrypsin
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longer, hydrophobic
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catalytic triad
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active site: aspartic acid, histidine, serine
-serine proteases |
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tetrahedral intermediate
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proteases
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aspartic protease active site
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2 asp residues
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mechanism of serine protease
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covalent intermediate
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mechanism of aspartic protease
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nu attack by water
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a proton is transferred between enzyme and substrate
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acid-base catalysis
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may use amino acids such as asp or lys for protonation or proton abstraction
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acid-base catalysis
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covalent bond forms between enzyme and substrate
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covalent catalysis
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uses nucleophilic functional group
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covalent catalysis
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two-part catalytic process
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covalent catalysis
-chymoptrypsin |
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catalysts may participate in redox reactions
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metal ion catalysis
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Zn2+ cofactor may properly orient substrate in active site through ionic interactions
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metal ion catalysis
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may take part in interactions involving Fe2+
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metal ion catalysis
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inverted repeat
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recognition site of restriction endonuclease
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control by modulators
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-feedback inhibition
-allosteric regulation |
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control by covalent modification
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-zymogen activation
-regulation of chymotrypsin -phosphorylation of glycogen phosphorylase |
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genetic control
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enzyme induction (synthesis)
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lactose stimulation of bacterial beta-galactosidase
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genetic control
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regulation of chymotrypsin
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control by covalent modification
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phosphorylation of glycogen phosphorylase
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control by covalent modification
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allosteric enzymes
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-interconvert between more/less active form (concerted model)
-may have binding sites for regulatory molecules separate from active sites -sigmoidal (S-shaped curve of V0 vs [S] -multiple subunit proteins |
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michaelis-menten kinetics
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-hyperbolic curve
-more active enzyme |
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isozymes
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-present in various developmental stages
-different amino acid sequences -lactate dehydrogenase |
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kinases
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-catalyze phosphorylation reactions
-may use ATP as phosphoryl group donor |
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phosphatases
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-remove phosphoryl groups from proteins: dephosphorylation
-turn off signaling pathways triggered by kinases -NOT the reverse of phosphorylation |
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master activator in digestion
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enteropeptidase
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pancreatic zymogens directly activated by trypsin
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-procarbozypeptidase
-chymotrypsinogen -proelastase -prolipase |
