ENZYMES

PRESENTATION ON FOOD CHEMISTRYAND MICROBIOLOGY1Submitted by:RESHMA AHMED BARLASKARNISHAR ABID MAZUMDERSARBANI RANI DEBJANIS AKHTAR BARBHUIYAKAKALI BAISHNAB.

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TOPIC:

ENZYMES AND VITAMINS3ENZYMESThese are proteins with catalytic properties due to their power of specific activation.Enzymes are proteins that increase the rate of reaction by lowering the activation energy.They catalyze nearly all the chemical reactions taking place in the cells of the body.Enzymes have unique three-dimensional shapes that fit the shapes of reactants (substrates)

44ENZYMES AS BIOLOGICAL CATALYSTS

5Chemical reactionsChemical reactions need an initial input of energy = THE ACTIVATION ENERGYDuring this part of the reaction the molecules are said to be in a transition state.

6Making reactions go fasterIncreasing the temperature make molecules move faster Biological systems are very sensitive to temperature changes.Enzymes can increase the rate of reactions without increasing the temperature. They do this by lowering the activation energy. They create a new reaction pathway a short cut .Enzyme controlled reactions proceed 108 to 1011 times faster than corresponding non- enzymic reactions.7An enzyme controlled pathway

8Classification of Enzymes ClassReactions catalyzedOxidoreductasesOxidation-reductionTransferasesTransfer groups of atomsHydrolases HydrolysisLyasesAdd atoms/remove atoms to/from a double bondIsomerasesRearrange atomsLigasesUse ATP to combine molecules

9The substrate The substrate of an enzyme are the reactants that are activated by the enzyme Enzymes are specific to their substratesThe specificity is determined by the active site.

10CofactorsAn additional non-protein molecule that is needed by some enzymes to help the reaction.

Tightly bound cofactors are called prosthetic groups

Cofactors that are bound and released easily are called coenzymes

Many vitamins are coenzymes.

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Active Site of an EnzymeThe active site is a region within an enzyme that fits the shape of substrate moleculesThe shape and the chemical environment inside the active site permits a chemical reaction to proceed more easily.Example: Amino acid side-chains align to bind the substrate through H-bonding, salt-bridges, hydrophobic interactions, etc. Products are released when the reaction is complete (they no longer fit well in the active site).

12Enzyme SpecificityEnzymes have varying degrees of specificity for substratesEnzymes may recognize and catalyze:- a single substrate- a group of similar substrates- a particular type of bond

13Lock-and-Key Model EMIL FISCHER gave this model.In the lock-and-key model of enzyme action: - the active site has a rigid shape- only substrates with the matching shape can fit- the substrate is a key that fits the lock of the active site.This is an older model, however, and does not work for all enzymes.S=substrate; E=Enzyme. E+S=Enzyme substrate complex.

EssEs14Induced Fit ModelIn the induced-fit model of enzyme action:- the active site is flexible, not rigid- the shapes of the enzyme, active site, and substrate adjust to maximumize the fit, which improves catalysis.- there is a greater range of substrate specificityThis model is more consistent with a wider range of enzymes.

15Induced Fit Model

16Factors affecting EnzymesSubstrate concentrationpHTemperatureInhibitors

17The effect of temperatureFor most enzymes the optimum temperature is about 30CMany are a lot lower, cold water fish will die at 30C because their enzymes denatureA few bacteria have enzymes that can withstand very high temperatures up to 100C.Most enzymes however are fully denatured at 70C.

18Temperature / CEnzyme activity01020304050Q10Denaturation19Inhibitors:Inhibitors are chemicals that reduce the rate of enzymic reactions.They are usually specific and they work at low concentrations.They block the enzyme but they do not usually destroy it. Many drugs and poisons are inhibitors of enzymes in the nervous system.

20The effect of enzyme inhibition:

Irreversible inhibitors :Combine with the functional groups of the amino acids in the active site, irreversibly.Examples: nerve gases and pesticides, containing organophosphorus, combine with serine residues in the enzyme acetylcholine esterase.Reversible inhibitors: These can be washed out of the solution of enzyme by dialysis. There are two categories.COMPETATIVENON COMPETATIVE

21 1.Competitive: These compete with the substrate molecules for the active site.The inhibitors action is proportional to its concentration.Resembles the substrates structure closely.2,Non-competitive: These are not influenced by the concentration of the substrate. It inhibits by binding irreversibly to the enzyme but not at the active site.Examples Cyanide combines with the Iron in the enzymes cytochrome oxidase.Heavy metals, Ag or Hg, combine with SH groups. These can be removed by using a chelating agent such as EDTA.

22COMPETETIVE INHIBITION1.

2323Non Competitive

2425VitaminsBiochem 3070 - Vitamins - EWalker11/22/201425Vitamins are necessary components of healthy diets and play important roles in cellular metabolism.Vitamins are considered micronutrients.Although these substances occur in only very small amounts within cells, they are critically important. Their absence is usually manifested as some deficiency disease.Vitamins are relatively small molecules that function most often as coenzymes.Humans must consume at least 12 vitamins in their diet, because we lack the ability to synthesize them.A well-balanced diet from a variety of food sources usually provides all these vitamins. However, many people supplement their diet with extra vitamins.

26What are Vitamins?

Some vitamins are measured in I.U.s (International Units), which is a measure of biological activity.

This measuring system is needed because these vitamins have several natural forms that have different activities on an equal weight basis.

Other vitamins are measured on the basis of weight (mg or g).27VITAMINS IUs Vitamins are categorized into two groups:Water soluble vitamins:The B-vitaminsVitamin CPantothenic acidBiotinFolic acidFat-soluble Vitamins:Vitamins A, D, E, K28Classification of vitamins

29Water soluble Vitamins

30Water-soluble Vitamins Structures of Water-soluble Vitamins

31Vitamin B12 The most complex structure of all vitaminsVitamin B12 is the most complex vitamin (with respect to its structure.)A colbalt ion is chelated at the center of this vitamin.Only 6g/day for an average adult helps prevent pernicious anemia. (One gram can supply 166,000 people!)

The current cost for this vitamin runs approximately $6,500 per kg.

32Vitamin CThe most recognized of all vitamins is Vitamin C (ascorbic acid):Ascorbic acid helps prevent scurvy, hence its name as the anti-scurvy or a-scorbic vitamin.

Scurvy is characterized by swollen and bleeding gums and subdermal haemorrhages

Connective tissue contains collagen protein. Collagen is a triple polypeptide helix that is strengthened by a significant quantity of 4-hydroxyproline.

Vitamin C is required to synthesize this important amino acid. Without it, connective tissues weaken, a condition often manifested as bleeding gums and other hemorrhagic tissues.33Vitamin C

34Fat-soluble VitaminsThe fat-soluble vitamins share some structural and solubility similarities.

35Fat-soluble VitaminsThe function and deficiency of A and E are switched.

36Vitamin AVitamin A Our visual pigment:Vitamin A helps with our vision.Too much Vitamin A can cause serious side effects, hence larger doses of this pure vitamin are controlled by prescription.Night blindness,Follicular hyperkeratosis,xeropthalmia occurs due to its deficiency.

37Vitamin D acts as a hormone, helping regulate the uptake of calcium from the intestines by promoting the synthesis of calcium-binding protein in the mucosal cells. Deficiency of this vitamin causes rickets, a condition of low levels of calcium, which results in soft and pliable bones, leading to bending and distortion.

Vitamin E is an excellent antioxidant. Therefore its primary use is in helping to promote shelf life of commercially important oils like cooking oils, lotions, etc.Much more Vitamin E is sold as a preservative than for use in vitamin supplements.Maintenance of nervous tissue and immune function.Role in iron metabolism.Helps vitamin A absorption.

Vitamin E38Sources of Vitamin E:

Hemolytic anemia.Hemolysis occurs in preterm infants because they did not receive enough vitamin E from their mothers.Preemie formulas and supplements compensate for increased needs.

Deficiency of Vitamin E:39

Family of compounds found in plants, plant oils, fish oils, and meatsSynthesized by the bacteria in the colon and are absorbed (10% of needs)

Role of Vitamin KRole in the coagulation processContributes to the synthesis of several blood-clotting factorsHelps form proteins present in bone, muscle, and kidneysImparts calcium-binding potentialPoor intake linked to increase in hip fractures.Deficiency of it are: gum bleeding, nose bleeding, malformed fingers,anaemia.

Vitamin K (Koagulation)4041THANK YOU