Enzymes Flashcards
Enzymes are predominantly protein in nature with the exception of _____
ribozymes
Enzymes increase the rate of a reaction by ___ to ___
10^9 - 10^20
Protein part of an enzyme
Apoenzyme
Non-protein portion of an enzyme that is necessary for catalytic function
Cofactor
Examples of cofactor (2)
Zn2+ and Mg2+
Non-protein organic molecule, frequently a B vitamin, that acts as a cofactor
Coenzyme
Compound/s whose reaction an enzyme catalyzes
Substrate
Specific portion of the enzyme to which a substrate binds during reaction
Active site
Any process that initiates or increases the activity of an enzyme
Activation
Portion on the enzyme surface where inhibitors/activators bind to regular catalytic reactions
Allosteric site
Compounds that slows down the rate of the reaction
Inhibitor
Process that makes an active enzyme less active or inactive
Inhibition
_____ catalyzes the hydrolysis of peptide bonds formed by the carboxyl group of lysine and arginine
Trypsin
Effect of enzyme in the activation energy
Lower activation energy
A rigid three-dimensional body where the enzyme surface contains the active site
Lock-and-key model
The active site becomes modified to accommodate the substrate
Induced-fit model
Classification of enzyme: oxidation-reduction reaction
Oxidoreductases
Classification of enzyme: group transfer reactions
Transferases
Classification of enzyme: hydrolysis reactions
Hydrolases
Classification of enzyme: Addition of two groups to a C-C double bond, or removal of two groups to create a C-C double bone
Lyases
Classification of enzyme: isomerization reactions
Isomerases
Classification of enzyme: joining to two molecules
Ligases
Classification of enzyme: Pyruvate with NADH forms lactate with NAD+ through lactate dehydrogenase
Oxidoreductase
Classification of enzyme: Aspartate a-Ketogutarate to Oxaloacetate + Glutamate
Transferase
Classification of enzyme: Acetylcholine with H2O to Acetate + Choline through Acetylcholinesterease
Hydrolase
Classification of enzyme: cis-Aconitate to Isocitrate through Aconitase
Lyase
Classification of enzyme: a-D-Glucose-6-phosphate to a-D-Fructose-6-phosphate through Phosphohexose isomerase
Isomerase
Classification of enzyme: ATP + L-tyrosine + tRNA to L-tyrosyl-tRNA + AMP + PP through Tyrosine-tRNA synthetase
Ligase
Enzyme activity is affected by (5)
Enzyme concentration
Substrate concentration
Temperature
pH
Presence of inhibitors
Enzymes made of ribonucleic acid
Ribozymes
Three types of inhibitors
Competitive
Non-competitive
Uncompetitive
Type of inhibitor: when it enters the active site, the substrate cannot enter
Competitive
Type of inhibitor: the inhibitor binds itself to a site other than the active site (allosterism), thereby changing the conformation of the active site
Noncompetitive
Emphasize the shape of the active site (2)
Lock-and-key model and induced-fit model
Just ____ amino acids participate in the active site in more than ____ of the enzymes studies to date
5, 65
Amino acids that participate in active sites
His, Cys, Asp, Arg, Glu
An enzyme-regulation process where the product of a series of enzyme-catalyzed reactions inhibits an earlier reaction in the sequence
Feedback control
An inactive form of an enzyme that must have part of its polypeptide chain hydrolyzed and removed before it becomes active
Proenzyme (Zymogen)
Example of proenzyme
Trypsin (digestive enzyme)
Trypsin is sinthesized and stored as ____, which has no enzyme activity
Trypsinogen
Trypsinogen only becomes active only after a six-amino fragment is hydrolyzed and removed from the ______
N-terminal end of its chain
Removal of the fragment of trypsinogen changes ____ structure (2)
Primary and tertiary structure
Enzyme regulation based on an event occurring at a place other than the active site but that creates a change in the active site
Allosterism
Modulation: inhibition of an allosteric enzyme
Negative
Modulation: stimulation of allosteric enzyme
Positive
A substance that binds to an allosteric enzyme
Regulator
The process of affecting enzyme activity by covalently modifying it
Protein modification
Best known example of protein modification
Pyruvate kinase inactivated by phosphorylation to pyruvate kinase phosphate
An enzyme that occurs in multiple forms; each catalyzes the same reaction
Isoenzyme
Example of isoenzyme
Lactas dehydrogenase (LDH) catalyzes the oxidation of lactate to pyruvate
Enzyme used for hepatitis
Alanine amino-transferase (ALT)
Enzyme used for prostate cancer
Acid phosphatase
Enzyme used for Liver or bone disease
Alkaline phosphatase (ALP)
Enzyme used for pancreatic disease or mumps
Amylase
Enzyme used for heart attack or hepatitis
Aspartate amino-transferase
Enzyme used for heart attack (3)
Lactate dehydrogenase (LDH)
Creatine phosphokinase (CPK)
Phosphohexose isomerase (PHI)
A molecule whose shape mimics the transition state of a substrate
Transition state analog
Example of transition state analog
Proline racemase reaction (Pyrrole-2-carboxylate mimics the planar transition state)
An antibody that has catalytic activity because it was created using a transition state analog as an immunogen
Abzyme
