Enzymes Part 1 COURSE TITLE: BIOCHEMISTRY 1 COURSE CODE: BCHT 201 PLACEMENT/YEAR/LEVEL: 2nd Year/Level 4, 1st Semester M.F.Ullah, Ph.D Showket H.Bhat, PhD

Proteins  Enzymes are Proteins Catalyst  Act as Catalyst to accelerates a reaction  Not permanently  Not permanently changed/destroyed in the process 2

enzyme substrate The reactant on which the enzyme acts on is the substrate 3 Enzyme Substrate Joins

C. Classification of Enzymes 1) named and classified according to the substrate acted upon and the reaction catalyzed. 2) trivial names-- end in -ase -- urease, hexokinase. 3) named based on a formal systemic catalog (IUB) with six major classifications. (All enzymes should fall into one of these categories and all enzymes therefore have a formal name.)

Oxidoreductases Class 1. Oxidoreductases- catalyze redox processes Example: RCH 2 -OH  RCH=O Transferases Class 2. Transferases- transfer chemical groups from one molecule to another or to another part of the same molecule. O O Example: CH 3 -C-SCoA + XR  CH 3 -C-XR + HSCoA acetyl CoAacetyl group transferred

Hydrolases Class 3. Hydrolases- cleave a bond using water to produce two molecules from one. O H 2 O O example: --CNH-R  --C-OH + H 2 N-R cleavage of a peptide bond Lyases Class 4. Lyases- remove a group from or add a group to double bonds. H-X H X ---C=C---  ---C--C---

Isomerases Class 5. Isomerases- interconvert isomeric structures by molecular rearrangements. CH 3 CH 3 HC-OH HO-CH COOH COOH Ligases Class 6. Ligases -- join two separate molecules by the formation of a new chemical bond usually with energy supplied by the cleavage of an ATP. example: O ATP ADP+P i O - OOC-C-CH 3 + CO 2 - OOC-C-CH 2 -COO - pyruvate oxaloacetate enzyme = pyruvate carboxylase

 The substrate of an enzyme are the reactants that are activated by the enzyme  Enzymes are specific to the substrates

restricted region enzyme binds substrate  A restricted region of an enzyme molecule which binds to the substrate. 9 Enzyme Substrate Active Site

 Fit between the substrate and the active site of the enzyme is exact  Like a key fits into a lock very precisely  The key is similar to the enzyme and the substrate is similar to the lock.  Temporary structure called the enzyme-substrate complex formed  Products have a different shape from the substrate  Once formed, they are released from the active site  Leaving it free to become attached to another substrate

changeshapeenzyme’s active site  A change in the shape of an enzyme’s active site  Inducedsubstrate.  Induced by the substrate. Enzyme Active Site substrate induced fit

 Some enzymes can change their shape (conformation)  When a substrate combines with an enzyme, it induces a change in the enzyme’s shape  The active site is then moulded into a exact conformation  Making the chemical environment suitable for the reaction

 This explains the enzymes that can react with a range of substrates of similar types Hexokinase (a) without (b) with glucose substrate

 Three factors: 1.Environmental Conditions 2.Cofactors and Coenzymes 3.Enzyme Inhibitors 14

1. Extreme Temperature are the most dangerous 1. Extreme Temperature are the most dangerous - high temps denature (unfold) enzyme. - high temps may denature (unfold) the enzyme. - Optimum Temperature required For most enzymes the optimum temperature is about 30°C - - Most enzymes however are fully denatured at 70°C 2.Optimum pH (most like pH near neutral) - - Extreme pH levels will produce denaturation 3.Ionic concentration (salt ions)

 An additional non-protein molecule that is needed by some enzymes to help the reaction  Tightly bound cofactors are called prosthetic groups  Cofactors that are bound and released easily are called coenzymes 16