Enzymatic Catalysis, Catalytic Mechanisms 10| Tulane

Enzymatic Catalysis, Catalytic Mechanisms

1.General Properties of Enzymes
2.Activation Energy and the Reaction Coordinate
3.Catalytic Mechanisms4.Serine Proteases (pp. 342-347)

• Give examples of various levels of substrate specificity, and explain specificity differences exhibited by serine proteases
• Give examples of reactions that utilize coenzymes NAD, FAD, Coenzyme A, and lipoic acid (metabolism lectures), and specify the role of the coenzyme
• Describe catalysis in terms of a reaction-coordinate energy diagram
• Classify enzymes by type of reaction
• Explain catalysis by enzymes in terms of chemical mechanisms
• Elaborate the catalytic mechanism of a chymotrypsin
• Explain divergent and convergent evolution
• Discuss the similarity of primary structure vs. tertiary structure in proteins as evidence supporting the existence of homology

Enzymes differ from chemical catalysts

• rates↑; Reaction specifity↑
• Mider reaction conditions
• Capacity for regulation

How Enzymes Work

• trhough the foramtion of weak bonds between the enzyem and the substrate.
• help arrange the substrate in a position favorable for reaction

Catalysis by Transition-state Stabilization

CH_3_ than H, rate increased 315 times: transition-state stabilization
Carbon -> Aceessi for the hydroxyl group;

L-Proline → [Planar transition stte] → D-Proline
L-Proline : 109.5°; transition state: 20°

I have no chemical background, so go on hell
I am so tird. Thats increadible. Let’s keep type so I do fall into sleep.

alkane → ahlcohole → aldchyl → Exrebexyl
R-CH₃ → R - CH₂OH → R-CH=O → R-C=C=H

---

Substrate Specificity

1. Lock Key model:
   • Hexokinase: 6C sugure, glucose, very specifics.
   • Founder: Fisher (Projection)
   • Enzyme distinguish different sugar model
2. Something like Ahlcohole Dehydrase methanol, Ethanol
   • Methanol → Carboxyl acid (toxity)
   • Drinking Ethanol to inhibitor Methanol metabolism

Example of “high” specificity (stereospecificity)

Citrate ←(Aconitase)→ Isocitrate

Enzyme is so large to interacte with the complex.

If you rotated the molecue,

Example of “low” specificity (geometric)

Chymotrypsin:

• Peptide: RCO::NHR' + H₂O → RCOO¯ + H₃N⁺R'
• Ester: RCO::OR' + H₂O → RCOO¯ + HOR' + H¯

Trypsin; Elastase

Example of enzyme that uses a coenzyme/cosubstrate

Ethano ←(ADH)→ Acetaldehyde

Adenosine: Oxidized Form ←→ Reduced Form

NAD⁺ \ NADP⁺
V_B, whichi needs by Mitochondria: nicotinamide riboside

As aging, the V_B gets low, supply in precouser to aging mouse, mitochondria could,
In humane: hearing lost in loud noise rescue.

Acid-base Catatlysis

Keto →	Transition state	→ Enol
	Form 1
	Form 2 + Acide
	Form 3 + Base

Different forms has difference entropy.

© Britannica

Covalent Catatlysis

© smu.edu

Metal Ion Catalysis

Zn Coordinate with His to do complex things.

Catalysis by Proximity and Orientation

Catalytic triad of chymotrypsin and other serine proteases

Serine protease mechanism (Exam)

Imtermider: not transition state, it is physical, detactable, and exist.S

© Maya Topf and W. Graham Richards

🐶 🐔

.