Lecture notes study book Harper's Illustrated Biochemistry Thirty-First Edition of Victor Rodwell, David Bender - ISBN: 9781259837944, Edition: 31, Year of publication: - (medicine notes)
1. Define the ff terms:
1.6. Metalloenzyme – roughly 1/3
1.1. Holoenzyme – apoenzyme + cofactor prosthetic group; - boud metal ions (prosthetic groups)
catalytically active enzyme cofactor complex - metal activated enzymes – metal ion cofactor
1.2. Apoenzyme – protein part; catalytically inactive; 1.7. Ribozyme – catalytic RNA molecules
requires cofactors (non-protein) - catalyze phosphodiester bonds of RNA
- non-protein enzyme
- RNA polymerase, ribonuclease
1.3. Zymogen – inactive; “precursor”; pepsinogen -> pepsin,
proinsulin -> insulin; prevents autodigestion of Co-factor
pancreas - transient, dissociable manner (binding)
- must be present in medium surrounding enzyme
1.4. Isoenzyme – arise through gene duplication for catalysis to occur
- sensitivity to particular regulatory factors - MC: metal ions
- substrate affinity
- ex. LDH (tetramer of heart muscle), CPK (dimer; Prosthetic groups
skeletal MM, cardiac MB) - tight, stable
- covalent / non covalent bonds
1.5. Coenzyme – non-protein, organic, assist enzymes in
transferring certain groups 2. Features of an enzyme as a catalyst
- transient, modified during reaction - Enzymes are neither consumed, nor permanently
- “recyclable shuttles” or group transfer reagents altered; highly efficient
- point of generation -> utilization - Extremely selective catalysts
- stabilizes H ions / Hydride ions o Reaction specific -> most important
- others: o Single substrate / closely related
o methyl groups (folates) substrate
o acyl groups (co-enzyme A) - Stereospecific catalysts
o oligosaccharides (dodichol) o Specific stereoisomers
3. Classes of enzymes
Code # Name Reaction involved Needs
coenzyme
1 Oxidoreductase - Red-ox Yes
- ex. Alcohol NAD oxidoreductase
2 Transferase - transfer of groups s.a. methyl or glycosyl groups from donor No
molecule to acceptor molecule
- ex. Hexokinase
3 Hydrolase - hydrolytic cleavage of C-C, C-O, C-N… Yes
- donor group transferred to H2O
- proteolytic enzymes – peptidases
- phosphatases – replace PO4 group
- add H2O across bond, hydrolyzing it
- carboxypeptidase A – cleavage of peptide bond
4 Lyases - catalytic cleavage of C-C, C-O, C-N by elimination, leaving
double bonds & add groups to double bonds
- add / remove elements of H2O, ammonia & CO2
- decarboxylases – remove CO2 from A or B keto acids / AA
- dehydratases – remove H2O to form dehydration rxn
5 Isomerases - geometric / structural changes w/in 1 molecule Yes
- cis-trans, aldose-ketose interconversions
- epimerase / racemerase – asymmetric C atoms
- mutases – intramolecular transfer; involve phosphorylated
enzyme
6 Ligases - joining together of 2 molecules, coupled to hydrolysis of
phosphoryl group in ATP or similar nucleoside triphosphate
-“high energy phosphate bond”
- synthases
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