5-Enzyme mechamism handout3

Rnase example 1 function structure reaction mechanism

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Unformatted text preview: pyrimidineorpurinecould substrate 3'nucleosidemonophosphateonly either2'or3'nucleoside monophosphate RNase: specificity Conclusions Enzymatic mechanism “cleaner” = more specific than chemical catalysis: • Specific phosphodiester linkages hydrolyzed. • Specific products formed. Enzyme-catalyzed reaction faster. Enzyme-catalyzed reaction has the “work-up” step built-in. Yet, the enzyme does accept the variety of RNA molecules required for its biological function. It is not too specific! Overview 1. Introduction: Thermodynamics vs. kinetics Catalysis Enzyme catalysis 2. RNase: (Example 1) Function, structure, reaction Mechanism without catalysis Transition state stabilization Acid/base catalysis Specificity 3. Chymotrypsin: (Example 2) Reaction cycle Covalent catalysis Acid/base catalysis Transition state stabilization Example 2: Chymotrypsin Three types of catalysis combined 1. Acid-base catalysis 2. Preferential binding of the transition state 3. Covalent catalysis 4. Metal ion catalysis 5. Proximity and orientation effects 2 substrate EScomplex 3 Allintermediatesinbetween. 3intermediates nzyme product#1 Chymotrypsin reaction cycle 4 EPcomplex product#2 7 6 5 Overview 1. Introduction: Thermodynamics vs. kinetics Catalysis Enzyme catalysis 2. RNase: (Example 1) Function, structure, reaction Mechanism without catalysis Transition state sta...
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