Presentation is loading. Please wait.

Presentation is loading. Please wait.

The Chemical Nature of Enzyme Catalysis POLAR NON- POLAR Tyr*His Gly AcidicNeutralBasic Asp Glu Gln Cys Asn Ser* Thr* Lys Arg Ala Val Ile Leu Met Phe Trp.

Similar presentations


Presentation on theme: "The Chemical Nature of Enzyme Catalysis POLAR NON- POLAR Tyr*His Gly AcidicNeutralBasic Asp Glu Gln Cys Asn Ser* Thr* Lys Arg Ala Val Ile Leu Met Phe Trp."— Presentation transcript:

1 The Chemical Nature of Enzyme Catalysis POLAR NON- POLAR Tyr*His Gly AcidicNeutralBasic Asp Glu Gln Cys Asn Ser* Thr* Lys Arg Ala Val Ile Leu Met Phe Trp Pro *OH

2 Amino acids

3 Acid-Base Catalysis Covalent catalysis: Nucleophilic catalysis Metal ion catalysis Electrostatic catalysis Transition state binding Proximity-Orientation effect Enzyme Catalysis

4 Acid-Base Catalysis An acid is a "proton donor" and a base is a "proton acceptor” In acid catalysis and base catalysis a chemical reaction is catalyzed by an acid or a base.

5 H O H Acid-Base Catalysis C O = NHNH HCHHCH NHNH + C - O O H O H -d-d +d+d H O H C O = NHNH HCHHCH C O = NHNH HCHHCH C O = NHNH HCHHCH Acid-base Catalysis Acid catalysis Base catalysis Both NHNH + C - O O H O H Ketoenol Slow Fast Very Fast

6 Acid-Base Catalysis Hydrolases: Hydrolysis of esters, peptides, phosphate Isomerases: Tautomesism (keto enol; amino:imino) Side chains of Asp/Glu/ His/Cys/Tyr/Lys act as general acid/base

7 Covalent catalysis: Nucleophilic catalysis Decarboxylation of acetoacetate in to acetone

8 Covalent catalysis: Nucleophilic catalysis 1.The enzyme forms a covalent bond to the substrate at some point during reaction 2.Lysine in the active site forms a Schiff base with the acetoacetate. (amine nucleophilically attack carboxyl group) 3.The positive charge of the Schiff base then facilitates decarboxylation (new electrophilic group withdraw electron from reaction centre)

9 Covalent catalysis: Nucleophilic catalysis

10

11 Activity Regulation: Metal ion catalysis

12 Metal ion catalysis 1.Bind to substrate for proper orientation 2.Mediate oxidation reduction reaction 3.Metal-Electrostatic catalysis Metal-Electrostatic catalysis 1.Charge stablization (similar to or better than Proton (pH not altered & >1charge 2.Promote nucleophilic cartalysis 3.Promote reaction through charge shielding

13 Metal ion catalysis: Charge stablization

14 Metal ion catalysis: nucleophilic cartalysis OH - is a weak nucleophilic agent but in presence of Zn it becomes a good nucleophilic

15 Nucleophilic cartalysis: carboxypeptidase

16 Activity Regulation: Electrostatic catalysis

17 Electrostatic catalysis: serine protease Ser 195 His 57 Asp 102 H–O–CH 2 O C–O - = Active Ser H–N N CC C H H CH 2 Ser 195 His 57 Asp O–CH 2 O C–O–H = N N–H CC C H H CH 2

18 Substrate If enzyme just binds substrate then there will be no further reaction Transition stateProduct Enzyme not only recognizes substrate, but also induces the formation of transition state X Activity Regulation: transition state binding

19

20 Preferred binding of the transition state complex Transition state analogues are competitive inhibitors

21 Activity Regulation: Proximity-Orientation effect


Download ppt "The Chemical Nature of Enzyme Catalysis POLAR NON- POLAR Tyr*His Gly AcidicNeutralBasic Asp Glu Gln Cys Asn Ser* Thr* Lys Arg Ala Val Ile Leu Met Phe Trp."

Similar presentations


Ads by Google