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what are isozymes
enzymes that have multiple forms, is different in structure, but catalyze the same reactions
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what are nonfunctional plasma enzymes
- enzymes with no physiologic function even with substrate present.
- Presence of these enzymes may reflect destruction of cells, from which they originate
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clinical use of acid pohsphatase
carcinoma of prostate
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clinical use of alanine aminotransferase (ALT)
hepatitis
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clinical use of alkaline phosphatase
bone disorders; obstructuive liver disease
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clinical use of amylase
acute pancreatitis
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clinical use of ceruloplasmin
wilson's disease
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clinical use of glutamyl transpeptidase
liver disease
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what are the isozymes that indicate myocardial infarction
- creatinine phosphokinase (CPK): MB isozyme appears w'in 24 hrs, normal in 48 hrs
- lactate dehydrogenase (LDH): H4 isozyme present for 2 wks
- Asparatate amino Transferase (AST): peaks at 2 days, normal by 4 days
- cardiac troponins (T and I): appears first w/in 4-6 hrs, may be high for up to 2 weeks
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clinical use of lipase
acute pancreatitis
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what are the dimer subunits of creatinine phosphokinase (CPK)
- MM isozyme - muscle
- BB isozyme - brain
- MB isozyme - heart
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what are the simer subunits of lactate dehydrogenase (LDH)
- H4 isozyme - heart (aerobic)
- M4 isozyme - muscle (anaerobic)
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what is the clinical significance of troponin
T and I are cardiac regulatory proteins that control the calcium mediated interaction between actin and myosin
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what is the clinical correlate for amylase
breaks down starch to glucose
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what are the 5 forms of enzyme regulation
- substrate availability
- allosteric regulation
- post translational modification
- interaction of control proteins
- zymogens
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describe substrate availability in terms of enzyme regulation
activity determined by concentration of substrate. not enough substrate won't allow enzyme to activate
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describe allosteric regulation in terms of enzyme regulation
when non competitive inhibitor binds to the allosteric site this inhibits the binding of substrate at active site
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describe relaxed state enzyme and tense state enzyme
- relaxed state - active enzyme (high affinity for substrate)
- tense state - inactive enzyme (low affinity for substrate
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describe post translational modification in terms of enzyme regulation
ex)?
- a modification in a protein by the covalent attachment of a chemical group to the amino acid
- ex. phosphorylation, acylation, hydroxylation
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describe interactions with control proteins in terms of enzyme regulation
- attachment of inhibitory subunit (protein) that deactivates the enzyme
- ex. cyclic AMP
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describe zymogens in terms of enzyme regulation
- zymogens: an inactive substance that is converted into an enzyme when activated by another enzyme.
- The enzymes are activated by the removal of a portion of the peptide chain (proteolysis)
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