EnzymesEnzymes

Functions and ControlFunctions and Control

Enzyme TermsEnzyme Terms

Substrate - the material and enzyme Substrate - the material and enzyme works on.works on.

Enzyme names: Ex. SucraseEnzyme names: Ex. Sucrase

- ase name of an enzyme- ase name of an enzyme

1st part tells what the substrate is. 1st part tells what the substrate is. (Sucrose)(Sucrose)

Enzyme NameEnzyme Name

Some older known enzymes don't fit this Some older known enzymes don't fit this naming pattern.naming pattern.

Examples: pepsin, trypsinExamples: pepsin, trypsin BUT…enzymes are proteins (-in = protein)BUT…enzymes are proteins (-in = protein)

Active SiteActive Site

The area of an enzyme that binds to the The area of an enzyme that binds to the substrate.substrate.

Structure is designed to fit the molecular Structure is designed to fit the molecular shape of the substrate.shape of the substrate.

Therefore, each enzyme is substrate Therefore, each enzyme is substrate specific.specific.

Models of How Enzymes Models of How Enzymes WorkWork

1. Lock and Key model1. Lock and Key model

2. Induced Fit model2. Induced Fit model

Lock and Key ModelLock and Key Model

Substrate (key) fits to the active site Substrate (key) fits to the active site (lock) which provides a microenvironment (lock) which provides a microenvironment for the specific reaction.for the specific reaction.

Induced Fit ModelInduced Fit Model

Substrate “almost” fits into the active site, Substrate “almost” fits into the active site, causing a strain on the chemical bonds, causing a strain on the chemical bonds, allowing the reaction to proceed.allowing the reaction to proceed.

Substrate

Active Site

Factors that Affect Factors that Affect EnzymesEnzymes

EnvironmentEnvironment CofactorsCofactors CoenzymesCoenzymes InhibitorsInhibitors Allosteric SitesAllosteric Sites

EnvironmentEnvironment

Factors that change protein structure Factors that change protein structure (denature) will affect an enzyme.(denature) will affect an enzyme.

Examples:Examples: pH shiftspH shifts temperaturetemperature salt concentrationssalt concentrations

CofactorsCofactors

Non-protein helpers for catalytic activity.Non-protein helpers for catalytic activity. Examples:Examples:

IronIron ZincZinc CopperCopper

CoenzymesCoenzymes

Organic molecules that affect catalytic Organic molecules that affect catalytic activity.activity.

Examples:Examples: vitaminsvitamins

Enzyme InhibitorsEnzyme Inhibitors

CompetitiveCompetitive - mimic the substrate and - mimic the substrate and bind to the active site.bind to the active site.

NoncompetitiveNoncompetitive - bind to some other part - bind to some other part of the enzyme.of the enzyme.

Allosteric RegulationAllosteric Regulation

Cell’s can’t have enzymes turned on all Cell’s can’t have enzymes turned on all the timethe time

The control of an enzyme complex by the The control of an enzyme complex by the binding of a regulatory molecule.binding of a regulatory molecule.

Regulatory molecule may stimulate or Regulatory molecule may stimulate or inhibit the enzyme complex by causing it inhibit the enzyme complex by causing it to change shape.to change shape.

Works like a reversible non-competitive Works like a reversible non-competitive inhibitorinhibitor

Allosteric RegulationAllosteric Regulation

Feedback InhibitionFeedback Inhibition

The end product of a metabolic pathway The end product of a metabolic pathway affects the function of an enzymeaffects the function of an enzyme

A metabolic pathway is switched off by A metabolic pathway is switched off by the inhibitory binding of its end product to the inhibitory binding of its end product to an enzyme that acts early in the pathwayan enzyme that acts early in the pathway

Usually allosteric regulationUsually allosteric regulation