Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik.

Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – 422222, India

SEP-SBI091-CP1-04 Introduction Programmes and Courses SEP–SBI091- U01 -CP1_04

School of Science and Technology, Online Counseling Resource… Credits  Academic Inputs by Sonali Alkari Faculty YCMOU Nagpur Centre, Faculty LAD college P.G. D of Biotechnology Research officer Ankur Seeds Pvt Ltd sonalisa_alkari@yahoo.co.in Sonalisaal@rediffmail.com 3 © 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved. 4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam.

School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to : Describe Physical and Chemical characteristics of enzymes Describe effect of pH, Describe effect of Temperature and others

School of Science and Technology, Online Counseling Resource… 6 Factors affecting enzyme activity 1.Enzyme & Substrate concentration 2.Cofactors 3.Inhibitors and activators © 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Enzyme concentration  In order to study the effect of increasing the enzyme concentration upon the reaction rate, the substrate must be present in an excess amount; i.e., the reaction must be independent of the substrate concentration.  Any change in the amount of product formed over a specified period of time will be dependent upon the level of enzyme present.  The amount of enzyme present in a reaction is measured by the activity it catalyzes. The relationship between activity and concentration is affected by many factors such as temperature, pH, etc. © 2008, YCMOU. All Rights Reserved.7

School of Science and Technology, Online Counseling Resource… Substrate concentration-1  With fixed enzyme concentration, an increase of substrate will result at first in a very rapid rise in velocity or rate of reaction.  As substrate concentration continues to increase, however the increase in the rate of reaction begins to slow down until, with a large substrate concentration, no further change in velocity is observed.  Enzyme-cataylzed reaction at varying substrate concentration the active sites on the enzyme molecules are not saturated by substrate and thus the enzyme rate varies with substrate concentration. © 2008, YCMOU. All Rights Reserved.9

School of Science and Technology, Online Counseling Resource… Substrate concentration-2  As the substrate molecule increases, the sites are covered to a greater degree until at saturation no more sites are available, the enzyme is working at full capacity and now the rate is independent of substrate concentration. © 2008, YCMOU. All Rights Reserved.10

School of Science and Technology, Online Counseling Resource… Substrate concentration-6 Why does the rate (velocity) of the reaction increase then appear to reach a plateau? 14 If the breakdown of the enzyme-substrate (ES) complex is rate limiting the v t will plateau out. © 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Substrate concentration-8 The shape of the curve and the kinetics of enzymes are modelled (described) by the equation below: 16© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Substrate concentration-9 1. What is V max ? V max is the maximum theoretical velocity of the reaction. 2. What is K m ? K m is a measure of the affinity of an enzyme for a given substrate. Functionally it is the [S] which gives 0.5 x Vmax. 17© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… 20 Problem!  The curve never really reaches a plateau so we cannot accurately determine V MAX.  If we cannot determine the V MAX then we cannot determine the K M. © 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… 21 How to measure these constants?  Several methods are availble; Lineweaver-Burk Plot Eddie-Hofstee Plot Hanes Plot Computer programs Other methods (http://www.sbu.ac.uk/biology/enztech/dete rmination.html) © 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Cofactors  Many enzymes need factors other than polypeptide molecules for full activity.  Prosthetic groups  Organic molecules tightly bound to the enzyme.  Flavin adenine dinucleotide (FAD) of succinate dehydrogenase.  Biotin of carboxylases e.g. pyruvate carboxylase. 25© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Cofactors Coenzymes  Organic molecules loosely associated with the enzyme.  NAD + or NADP + in enzymes catalysing redox reactions e.g. dehydrogenases. 26© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Inhibitors, inducers and activators Activators: increase the activity of an enzyme e.g. ADP is an activator of PFK. Inducers: switch on (induce) the synthesis of an enzyme e.g. lactose induces the enzyme - galactosidase. Inhibitors: inhibit (decrease) the activity of enzyme molecules. 28© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Inhibitors There are three types of enzyme inhibitors: 1.Competitive inhibitors 2. Non-competitive inhibitors 3. Un-competitive inhibitors Excess substrate can inhibit enzyme activity - in this case substrate molecules bind to another site causing inhibition. 29© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Competitive Inhibitors  As the name suggests competitive inhibitors compete with the substrate at the substrate- binding site.  The increase the K m but leave the V max unaffected.  E.g. malonate is a competitive inhibitor of succinate dehydrogenase. 30© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Non-competitive Inhibitors  Non-competitive inhibitors bind at a site away from the substrate-binding site. The affect V max but do not affect K m.  E.g. the heavy metal ions Hg 2+ and Pb 2+ are non-competitive inhibitors.  They are thought to bind to -SH groups within the enzyme. 32© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Enzyme Activity Depends on Ph-1  Enzymes have an optimum pH (or pH range) at which their activity is maximal; at higher or lowerpH, activity decreases. This is not surprising.  Amino acid side chains in the active site may act as weak acids and bases with critical functions that depend on their maintaininga certain state of ionization, and elsewhere in the protein ionized side chains may play an essential role in the interactions that maintain protein structure.  Removing a proton from a His residue, for example, might eliminate an ionic interaction essential for stabilizing the active conformation of the enzyme. © 2008, YCMOU. All Rights Reserved.35

School of Science and Technology, Online Counseling Resource… Enzyme Activity Depends on pH-2  A less common cause of pH sensitivity is titration of a group on the substrate.  The pH range over which an enzyme undergoes changes in activity can provide a clue to the type of amino acid residue involved.  A change in activity near pH 7.0, for example, often reflects titration of a His residue.  The effects of pH must be interpreted with some caution, however.  In the closely packed environment of a protein, the pKa of amino acid side chains can be significantly altered. © 2008, YCMOU. All Rights Reserved.36

School of Science and Technology, Online Counseling Resource… Enzyme Activity Depends on pH-3  For example, a near by positive charge can lower the pKa of a Lysresidue, and a nearby negative charge can increase it.  Such effects sometimes result in a pKa that is shifted by several pH units from its value in the free amino acid.  In the enzyme acetoacetate decarboxylase, for example,one Lys residue has a pKa of 6.6 (compared with 10.5in free lysine) due to electrostatic effects of nearby positive charges. © 2008, YCMOU. All Rights Reserved.37

School of Science and Technology, Online Counseling Resource… Effect of Temperature  Because of the protein nature of an enzyme thermal denaturation of the enzyme protein with increasing temperatures will decrease the effective concentration of an enzyme and consequently decrease the reaction rate.  Up to perhaps 45 0 C the predominant effect will be an increase in reaction rate as predicated by kinetic theory.  Above 45 0 C an opposing factor, namely thermal denaturation will become increasingly important, however, until at 55 0 C rapid denaturation will destroy the catalytic function of the enzyme protein. © 2008, YCMOU. All Rights Reserved.38

School of Science and Technology, Online Counseling Resource… What You Learn… The amount of enzyme present in a reaction is measured by the activity it catalyzes. The enzyme activity is dependent of substrate and enzyme concentration, cofactors, coenzymes and inhibitors. V max is the maximum theoretical velocity of the reaction. K m is a measure of the affinity of an enzyme for a given substrate. The change in pH and temperature alter the structure of enzyme. There are different types of inhibitors; competitive, non-competitive and uncompetitive. 39© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Critical Thinking Questions 1.What is the relationship between enzyme and substrate concentration and enzyme activity? 2. State different types of inhibitors? 3.What is the role of pH and temperature in enzyme activity? © 2008, YCMOU. All Rights Reserved.40

School of Science and Technology, Online Counseling Resource… Hints For Critical Thinking Question 1.Any change in the amount of product formed over a specified period of time will be dependent upon the level of enzyme and substrate present,V max, K m. 2.competitive, non-competitive and uncompetitive. 3.Denaturation of enzyme molecule take place in extreme condition of pH and temperature © 2008, YCMOU. All Rights Reserved.41

School of Science and Technology, Online Counseling Resource… Study Tips:1  Book1 Title: Molecular Cell Biology Author: Harvey Lodish, David Baltimore Publisher:Publishers: W. H. Freeman and Company  Book2 Title: Principles of Biochemistry Author: AlbertL Lehninger Publisher:CBS Publishers & Distributors 42© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Study Tips:2  Book3 Title: Biochemistry Author: Lubert stryer Publishers: Freeman International  Book4 Title: Biochemistry Author: Keshav Trehan Publishers: Wiley Eastern 43© 2008, YCMOU. All Rights Reserved.

School of Science and Technology, Online Counseling Resource… Study Tips www.en.wikipedia.org Microsoft Encarta Encyclopedia http://en.wikipedia.org/wiki/ Wikipedia the free encyclopedia (www.chem.qmul.ac.uk/iubmb/enzyme). 44© 2008, YCMOU. All Rights Reserved.

Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik.

Similar presentations

Presentation on theme: "Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik."— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik.

Similar presentations

Presentation on theme: "Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik."— Presentation transcript:

Similar presentations

About project

Feedback