结构生物化学Chapter8 Introduction to enzymology

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Enzyme catalyzed reactions display saturation kinetics with respect to reactant concentration
Important things to remember about enzymes just like other catalysts
1. Higher reaction rates: The rates of enzym
processes are accele8-r1 1 a. 00 ted by a Example1: carbonic anhydrase catalyzes: CO2 +H2O? H2CO3 nonenzymatic rate constant = 1.3 x 10-1 s-1 enzymatic rate constant = 1 x 106 s-1 (x 7.7 x 106) Example2: Staphylococcal nuclease catalyzes nucleic acid hydrolysis nonenzymatic rate constant = 1.7 x 10-13 s-1 enzymatic rate constant = 95 s-1 (x 5.6 x 1014)
? Enzyme catalyzed reactions ar uncatalyzed reactions.
? Enzyme catalyzed reactions di with respect to substrate conce
? Enzyme catalyzed reactions ar temperature and pH values.
? Catalytic RNA, or ribozymes, s criteria: substrate specificity emerge from reaction unchang
The difference between enzyme catalyzed & uncatalyzed chemical reactions
Chapter 8 Introduction to Enzymology
Outline
?What is enzyme? ?Chemical nature of enzymes ?Catalytic properties of enz
-Features shared by enzyme catalysts -Unique features of enzymes ?Classification and nomenclat
What is Enzymes?
?Enzymes are biological ca
the rates of c. hemical rea
Snail without enzyme catalySstnail with enzymபைடு நூலகம்
Substrates, products, and enzymes
Enzymes catalyze the rate converted to product
2. Enzymes catalyze both the forward and the reverse reaction.
? This is an important podientt. ermiAnne ewnhziycmhe the reaction goes, it only increases t equilibrium.
Enzyme
Substrates
Product
Enzymes catalyze the conversion of substrates into products
?What is a substrate? A substrate is the compound product in an enzyme cata For the reaction catalyze phosphate is the substrate.
Chemical nature of enzymes
? All enzymes are proteins exce proteins are enzymes
? It was assumed that all enzyme when Thomas Cech and Sydney Al catalytic RNAs (Nobel prize in
1. Enzymes are not consumed or altered by the reaction they catalyze.
? Just as a construction worker can take being physically changed by the proc them into products without being physic
Enzymes catalyze both the reactions in both the forward and reverse direction
LDH LDH
3. Enzymes do not alter the equilibrium (or equilibrium constant) between substrates and products.
Enzyme catalyzed reactions are much faster than uncatalyzed reactions
Enzyme catalyzed r eaction
[Product]
D[Product]
Reaction Rate = D(time)
Uncatalyzed
reaction
? At equilibrium, the ratio of substrate whether an enzyme catalyst is present. of reactants to products is not altered is achieved is increased.
General Properties of Enzymes