ภาควิชาเคมี คณะวิทยาศาสตร์ Lecture #6 เอนไซม์ ( ENZYMES) รศ.ดร. พรทิพย์ ชัยมณี ภาควิชาเคมี คณะวิทยาศาสตร์ มหาวิทยาลัยศิลปากร

The X-ray structure of HEW lysozyme Chemistry Science Silpakorn University Dr. Porntip Chaimanee

เอนไซม์ ( ENZYMES) 1. Properties of enzymes (คุณสมบัติของเอนไซม์) 2. Enzyme Kinetics (จลนพลศาสตร์ ของเอนไซม์) 3. Mechanism of enzyme catalysis (กลไกการเร่งปฏิกิริยา ของเอนไซม์) 4. Control of enzymes activity (การควบคุมการทำงานของ เอนไซม์) Chemistry Science Silpakorn University Dr. Porntip Chaimanee

คุณสมบัติเฉพาะของเอนไซม์ (Unique properties of enzyme) 1. มีประสิทธิภาพสูง (high efficiency) เพิ่มอัตราเร็วของปฎิกิริยา 106 -1012 ปฎิกิริยาดำเนินได้ในสภาวะปกติ 2. มีความจำเพาะสูง (high specificity) ต่อตัวทำปฎิกิริยา (substrate) ต่อชนิดของปฎิกิริยา (reaction) 3. ถูกควบคุมได้ (capacity to regulation) Chemistry Science Silpakorn University Dr. Porntip Chaimanee

ความสามารถในเร่งปฏิกิริยาของเอนไซม์บางชนิด (Catalytic powers of some enzymes) Enzyme Nonenzymatic Enzymatic Reaction Rate Reaction Rate(s-1) Rate (s-1) Enhancement Carbonic anhydrase 1.3 x 10-1 1 x 106 7.7 x 106 Lysozyme 3 x 10-9 5 x 10-1 1.6 x 108 Triose phasphate isomerase 4 x 10-6 4 x 103 1.0 x 109 Carboxypeptidase A 3 x 10-9 5.7 x 102 1.9 x 1011 Catalase 1 x 10-8 4 x 107 4 x 1015 Alkaline phosphatase 1 x 10-15 1 x 102 1 x 1017 Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Enzyme-substrate complex Chemistry Science Silpakorn University Dr. Porntip Chaimanee

International classification of enzymes Class Name Reaction type Example 1 Oxidoreductases Transfer of electron Ared + Box Aox +Bred Alcohol dehydrogenase 2 Transferases Transfer of functional group A-B + C A + B-C Hexokinase 3 Hydrolases Hydrolysis reaction A-B +H2O A-H + B-OH Trypsin 4 Lyases Cleavage of C-C,C-O,C-N A- B A=B + x-y Pyruvate decarboxylase and other bonds x y 5 Isomerases Transfer of groups A-B A-B Maleate isomerase within a molecule x y y x 6 Ligases Bond formation coupled A + B A-B Pyruvate carboxylase (or Synthases) to ATP hydrolysis Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Enzyme terminology EC.X.X.X.X Example EC.1.1.1.1 (Alcohol dehydrogenase) 1. Oxidoreductase ( enzyme catalyzing oxidation-reduction reaction) 1.1 Acting on CH-OH group of donors 1.1.1 With NAD+ or NADP+ as acceptor 1.1.1.1 Alcohol:NAD oxidoreductase Alcohol + NAD+ aldehyde or ketone + NADH + H+ Example EC.1.1.3.4 (Glucose oxidase) 1.1.3 With O2 as acceptor 1.1.3.4 b-D-glucose: oxygen oxidoreductase b-D-glucose + O2 D-glucono-d-lactone + H2O2 Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Activator ions Metal ions Cosubstrates Prosthetic groups Cofactors Essential ions Coenzymes Activator ions Metal ions Cosubstrates Prosthetic groups (loosely bound) (tightly bound) (loosely bound) (tightly bound) Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Elemental cofactors Element Enzyme Fe 2+ / Fe 3+ Cytochromes, peroxidases,catalases Cu + / Cu 2+ Cytochrome oxidase, tyrosidase Mg 2+ Most of the phosphotransferases Zn 2+ Alcohol dehydrogenase, carbonic anhydrase Se Glutathione peroxidase Cl - a-amylase Ni 2+ Urease Ca 2+ Phosphorylase kinase Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Coenzyme derivatives of some water-soluble vitamins Vitamin Coenzyme derivative Thiamine (vitamin B1) Thiamine pyrophosphate Riboflavin (vitamin B2) Flavine adenine dinucleotide and flavin mononucleotide Nicotinate (niacin) Nicotinamide adenine dinucleotide Pyridoxine,pyridoxal and Pyridoxal phosphate pyridoxamine(vitamin B6) Pantotinate Coenzyme A Biotin Covalently attached to carboxylases Folate Tetrahydrofolate Cobalamin(vitamin B12) Cobamide coenzymes Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Nicotinamide adenine dinucleotide (NAD+) Oxidized form Reduced form Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Structure of Lactate dehydrogenase (Tetramer 140 kDa) 1.1.1.27 Pyruvate Lactate NADH +H+ NAD+ Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Active site of Lactate dehydrogenase Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Redox coenzymes Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Nucleoside phosphate as coenzyme in phosphotransferases and ligases Adenylase kinase Adenylase kinase ATP + AMP ADP + ADP Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Group-transfering coenzymes I Chemistry Science Silpakorn University Dr. Porntip Chaimanee

Group-transfering coenzymes II Chemistry Science Silpakorn University Dr. Porntip Chaimanee