Microbial Metabolism Ch. 8- pg 216 Metabolism- Greek- to change Enzymes

What is metabolism? The sum of chemical reactions within a living organism The sum of chemical reactions within a living organism C 6 H 12 O 6 + 6O 2 6CO2 + 6H2O + energy H2OH2O O2O2 ATP NADH NAD + H+H+ e-e-

Why do we need to know about microbial metabolism? Metabolism is the basis of all life, not just microbes Metabolism is the basis of all life, not just microbes Metabolism forms the basis of all forms of microbiology from environmental microbiology to medical microbiology Metabolism forms the basis of all forms of microbiology from environmental microbiology to medical microbiology If your interest is in human health, knowledge of metabolism forms the basis of antibiotic therapy. Some antibiotics interfere with metabolic reactions If your interest is in human health, knowledge of metabolism forms the basis of antibiotic therapy. Some antibiotics interfere with metabolic reactions

Catabolic and Anabolic reactions Catabolism Catabolism degradative; breaks the bonds of larger molecules forming smaller molecules; releases energy degradative; breaks the bonds of larger molecules forming smaller molecules; releases energy Generally hydrolytic- absorbs water Generally hydrolytic- absorbs water exergonic (produce energy)-energy stored in chemical bonds is released exergonic (produce energy)-energy stored in chemical bonds is released Anabolism Anabolism biosynthesis; process that forms larger macromolecules from smaller molecules; requires energy input biosynthesis; process that forms larger macromolecules from smaller molecules; requires energy input Generally dehydration synthesis reactions (release water) Generally dehydration synthesis reactions (release water) Endergonic (consume energy) Endergonic (consume energy)

Enzymes-the driving force of metabolic reactions An enzyme is a biological catalyst that speeds up chemical reactions is the cell An enzyme is a biological catalyst that speeds up chemical reactions is the cell Increase the rate of a chemical reaction times – to the speed of life Increase the rate of a chemical reaction times – to the speed of life Specific for a particular substrate and reaction Specific for a particular substrate and reaction The unique three-dimensional shape of an enzyme allows it to recognize its substrate The unique three-dimensional shape of an enzyme allows it to recognize its substrate

How do enzymes work? Decrease the activation energy, the energy required to initiate a chemical reaction Decrease the activation energy, the energy required to initiate a chemical reaction Enzymes have an active site at which only specific reactants or substrates are positioned for various interactions. Enzymes have an active site at which only specific reactants or substrates are positioned for various interactions. Pg 219-text Pg 219-text

Enzyme-substrate interaction Active site

Turnover number Enzymes participate in chemical reactions but are not consumed by them (can function over and over again) Enzymes participate in chemical reactions but are not consumed by them (can function over and over again) An enzymes speed or turnover number is the maximum number of substrate molecules an enzyme molecule can convert to product each second An enzymes speed or turnover number is the maximum number of substrate molecules an enzyme molecule can convert to product each second Enzyme speeds can range over several orders of magnitude but are characteristic of a particular enzyme Enzyme speeds can range over several orders of magnitude but are characteristic of a particular enzyme Examples Examples DNA polymerase (DNA synthesis) 15 DNA polymerase (DNA synthesis) 15 Catalase (breakdown of H 2 O 2 ) 20,000 Catalase (breakdown of H 2 O 2 ) 20,000

Enzyme components Simple enzymes- consist entirely of protein Simple enzymes- consist entirely of protein Conjugated enzymes ( Holoenzyme )consist of: Conjugated enzymes ( Holoenzyme )consist of: Apoenzyme-the protein component Apoenzyme-the protein component Cofactor-non protein component Cofactor-non protein component metallic cofactors – iron, copper, magnesium, calcium metallic cofactors – iron, copper, magnesium, calcium vitamins, organic molecules (coenzyme) vitamins, organic molecules (coenzyme) Apoenzyme + cofactor = Holoenzyme Apoenzyme + cofactor = Holoenzyme In the absence of the cofactor, the apoenzyme is inactive In the absence of the cofactor, the apoenzyme is inactive

Coenzymes Coenzymes Can act in catalysis by accepting a chemical group from one substrate and transferring it to another substrate Can act in catalysis by accepting a chemical group from one substrate and transferring it to another substrate Some act as electron carriers Some act as electron carriers Many are derived from vitamins. Examples: Many are derived from vitamins. Examples: vitamin B 6 -coenzyme in amino acid metabolism, vitamin B 6 -coenzyme in amino acid metabolism, Folic acid-coenzyme in the synthesis of nucleotides Folic acid-coenzyme in the synthesis of nucleotides

Important coenzymes in cellular metabolism Nicotinamide adenine dinucleotide (NAD + ) Nicotinamide adenine dinucleotide (NAD + ) NAD + is involved in catabolic reactions NAD + is involved in catabolic reactions Nicotinamide adenine dinucleotide phosphate (NADP + ) Nicotinamide adenine dinucleotide phosphate (NADP + ) NADP + is involved in anabolic reactions NADP + is involved in anabolic reactions Both NAD+ and NADPH are derivatives of vitamin B 1 (niacin) and they both function as electron carriers Both NAD+ and NADPH are derivatives of vitamin B 1 (niacin) and they both function as electron carriers

Other key coenzymes The flavin coenzymes The flavin coenzymes Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) Derivatives of vitamin B 2 (riboflavin) Derivatives of vitamin B 2 (riboflavin) Also act as electron carriers Also act as electron carriers Coenzyme A Coenzyme A Derivative of vitamin B 5 (pantothenic acid) Derivative of vitamin B 5 (pantothenic acid) Important roles in fat metabolism and the TCA (Tricarboxylic Acid) cycle Important roles in fat metabolism and the TCA (Tricarboxylic Acid) cycle

Naming enzymes- substrate acted on or type of reaction Class (-”-ase”) Type of chemical reaction Oxidoreductase Oxidation-reduction (redox) reactions. Loss or gain of electrons. Transferase Transfer of functional groups, such as an amino or a phosphate group Hydrolase Cleaves bonds on molecules with the addition of water (hydrolysis) Lyase Removal or addition of groups of atoms without hydrolysis Isomerase Rearrangement of atoms within a molecule Ligase Joining two molecules (using energy from the breakdown of ATP) See pg 224- Microbits 8.3- The enzyme Name Game

Oxidation-Reduction Reactions Oxidation- loss or removal of electrons Oxidation- loss or removal of electrons Many substances combine with oxygen and transfer elections to oxygen. Substance becomes oxidized Many substances combine with oxygen and transfer elections to oxygen. Substance becomes oxidized If another electron receptor is present, oxygen does not need to be present. If another electron receptor is present, oxygen does not need to be present. Reduction- gain of electrons Reduction- gain of electrons Substance becomes reduced. Substance becomes reduced. Because oxidation and reduction must occur simultaneously, reactions of called redox reactions. Because oxidation and reduction must occur simultaneously, reactions of called redox reactions.

Comparison of oxidation and Reduction Oxidation Loss of electrons Loss of electrons Gain of oxygen Gain of oxygen Loss of hydrogen Loss of hydrogen Loss of energry-liberates energy Loss of energry-liberates energy Exothermic, exergonic Exothermic, exergonic Gives off heat Gives off heat Reduction Gain of electrons Loss of oxygen Gain of hydrogen Gain of energy- energy stored in reduced compound Endothermic; endergonic Requires energy, such as heat.

Factors affecting enzymatic activity -rate of chemical reactions increases with temperature -elevation above a certain temperature reduces enzymatic activity due to denaturation of the enzyme -most enzymes have a pH optimum -changes in pH can cause result in alterations in the 3D-structure of the enzyme leading to denaturation -high substrate concentration leads to maximal enzyme activity, the enzyme is said to be saturated -under normal conditions enzymes are not saturated

Exo and endoenzymes Exoenzymes Active outside the cell Active outside the cell Breakdown of nutrients that are too large to enter the cell. Breakdown of nutrients that are too large to enter the cell. Some play a role in disease e.g., Streptokinase; phospholipase C Some play a role in disease e.g., Streptokinase; phospholipase C Endoenzymes Most metabolic enzymes are endoenzymes Most metabolic enzymes are endoenzymes

Control of metabolic pathways Metabolic pathways are controlled at the level of their enzymes Metabolic pathways are controlled at the level of their enzymes Control of enzymes Control of enzymes Synthesis Synthesis Activity Activity

Production of enzymes in the cell Enzymes can be produced at constant levels in the cell (constitutive enzymes) OR Their production can be regulated in response to substrate( induced enzymes) or product concentrations (feedback mechanisms).

Constitutive enzymes – always present, always produced in equal amounts or at equal rates, regardless of amount of substrate Constitutive enzymes – always present, always produced in equal amounts or at equal rates, regardless of amount of substrate enzymes involved in glucose metabolism enzymes involved in glucose metabolism Regulated enzymes – not constantly present; production is turned on (induced) or turned off (repressed) in response to changes in concentration of the substrate Regulated enzymes – not constantly present; production is turned on (induced) or turned off (repressed) in response to changes in concentration of the substrate

Enzyme Inhibitors An effective way to control the growth of bacteria is to control their enzymes An effective way to control the growth of bacteria is to control their enzymes Certain poisons such as cyanide, arsenic and mercury combine with enzymes and inhibit their activity Certain poisons such as cyanide, arsenic and mercury combine with enzymes and inhibit their activity Enzyme inhibitors can be classed as Enzyme inhibitors can be classed as Competitive inhibitors Competitive inhibitors Noncompetitive inhibitors Noncompetitive inhibitors

Competitive inhibitors Fill the active site and compete with substrate Fill the active site and compete with substrate Similar in shape and chemical structure to the substrate Similar in shape and chemical structure to the substrate Does not undergo any reaction to form products Does not undergo any reaction to form products May bind reversibly or irreversibly. May bind reversibly or irreversibly. e.g., Inhibition of folic acid synthesis by sulfanilamide

Noncompetitive inhibitors Interact with a site other than the active site (allosteric or regulatory site) Interact with a site other than the active site (allosteric or regulatory site) Binding of the inhibitor causes a change in the shape of the active site, making it nonfunctional (allosteric inhibition) Binding of the inhibitor causes a change in the shape of the active site, making it nonfunctional (allosteric inhibition) May bind reversibly or irreversibly May bind reversibly or irreversibly

Enzyme Repression The end-product of the reaction signals back to the DNA to turn off expression of the gene The end-product of the reaction signals back to the DNA to turn off expression of the gene Prevents the cell from wasting energy Prevents the cell from wasting energy

The Cell’s Energy Machine