Samantha Scruggs
Flashcards by , created over 3 years ago

Chapter 10 in Textbook of Biochemistry with Clinical Correlations by Thomas M Devlin

Samantha Scruggs
Created by Samantha Scruggs over 3 years ago
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Question Answer
6 different types of enzymes 1. oxidoreductases 2. hydrolases 3. isomerases 4. transferases 5. lyases 6. ligases
isozymes different structural forms of a protein that catalyze the same reaction.
oxidoreductases catalyze oxidation-reduction reactions. Examples - dehydrogenases, oxidases, reductases, peroxidases, catalase, oxygenases, hydroxylases Electrons are removed from one substrate and added to another.
transferases transfer a chemical group from one molecule to another. Examples - transaldolase, transketolase, acyl, methyl, glucosyl and phosphoryltransferases, kinases, phosphomutases For example, aminotransferases transfer the amino group to convert an AA to a ketoacid. They require Vitamin B6
hydrolases catalyze hydrolysis reactions. examples: esterases, glycosidases, peptidases, phosphatases, thiolases, phospholipases, amidases, deaminases, ribonucleases transfer -OH from water to substrate. Irreversible reaction. Substrate is typically an ester or an amide.
lyases break apart a bond, usually a carbon-carbon bond. Can also be carbon-nitrogen, or release CO2 from a B-keto-acid. Examples - decarboyxlase, aldolases, hydratases, dehydratases, synthases, lyases if ATP is required, it's called synthetase. If not, it's synthase.
isomerases Involved with moving a group or a double bond within the same molecule. Examples: racemases, epimerases, isomerases, mutases (not all) Mutase is when a phosphate is moved from one carbon to another within the same molecule such as occurs with phosphglycerate mutase that converts 2-phosphoglycerate to 3-phosphoglycerate
ligases join carbon atoms together, but unlike lyases, they require energy for the reaction and are referred to as synthetases. Also carboxylases. Energy usually comes from ATP.
binding of a substrate by an enzyme for an enzyme to function as a catalyst (which increases the rate of the reaction, but does not change equilibrium or K), it must first bind the substrate and then lower the energy of activation so that the reaction will proceed at a faster rate than it would in the absence of the catalyst. Two prevalent theories exist to explain how substrates bind the enzyme - lock and key theory, and induced-fit theory
lock and key theory proposes that a binding site for substrate on the enzyme is a rigid entity and only a compound with a particular shape will fit, analogous to how a lock allows only one key to make the proper contact.
induced-fit theory Assumes that the enzyme is flexible, and after the substrate binds the enzyme, the conformation of the protein changes so that a stable binary complex forms.