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BIOCATALYSIS - Coggle Diagram
BIOCATALYSIS
ENZYME
” protein produced by the cell of living organism which act as biological catalysts by controlling & accelerating the rate of biochemical reaction in the cell at fairly low temperatures”
CHARACTERISTICS OF ENZYMES
- enzyme are globular proteins
- acts a biological catalysis
- enzymes are rigid
= enzyme limited to one specific reaction that involves a specific substrate only
= this nature of enzyme provides a precise control of reaction that occur in living system
- enzyme are not damaged by the reaction catalysed by them
= enzyme can be used repeatedly without being replaced
- enzyme can react in both direction
= enzyme only speed up the reaction not determine the direction of the reaction
= speed of reaction usually stated in turnover number which refer to the number of substrate molecules that are changed by an enzyme molecules to its products in one minute
= due to highly speed reaction, enzyme are needed in small quantities
CLASSIFICATION OF ENZYME
- OXIDOREDUCTASE
” transfer H or O atoms or electron from one molecules to another”
- TRANSFERASE
” transfer of a specific groups from one molecules to another. Group may be methyl-, acyl-, amino-, or phosphate”eg : transaminases and phosphorylase
- HYDROLASE
” formation of 2 products from a substrate by hydrolysis (splitting molecules with water)”eg : lipase, amylase and peptidases
- LYASE
” non-hydrolytic addition or removal of groups from substrate. C-C, C-N, C-O or C-S bond may be split”eg : decarboxylase and carboxylase
- ISOMERASE
“ intramolecular rearrangement one isomer converted into another”
- LIGASE
” join together two molecules by synthesis of new C-C, C-N, C-O or C-S bond by using energy from ATP”eg : synthetases and aminoacyl tRNA synthetases
ENERGY OF REACTION & CATALYSIS” energy required for a reactant or substrate to start a reaction”
- enzyme acts as biological catalyst which lower the activation energy needed so speed up the reaction
- without enzyme, all the reaction in living cell occur very slowly
CATALYSIS
” mechanism for a certain substances that is called catalyst to reduce the energy of activation and to start the reaction”
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ENZYME COFACTOR
- some enzyme need non-protein compound known as cofactor to bind with them before they catalyse a reaction
- enzyme-cofactor complex called holoenzym
- enzyme that doesnt have cofactor called apoenzyme
- 3 type of cofactors
a. prosthetic groups
b. coenzyme
c. metal ions (enzyme activators)
A. PROSTHETIC GROUP “ non-protein component which is strongly bound to an enzyme & become part of the enzymestructure and not easil separated”eg : FAD and haem
- FAD contain riboflavin (vitamin B2) which acts as the hydrogen accepting part in FAD
- Haem is an iron-containing prosthetic group and has a number of biological functions such as electron carrier and oxygen carrier
B. COENZYMES“ small, non-protein organic molecules that bind loosely and temporarily to active site of the enzyme”
- coenzyme readily detach & help to transfer chemical group, atoms or electron from one enzyme to another
- many coenzyme are derivatives of vitamins especially group b vitamins
eg : NAD is a form of niacin which is a coenzyme for a number of dehydrogenase enzyme and acts as hydrogen acceptor
C. METAL IONS”activators are inorganic ions such as Ca2+,Zn2+, Fe2+ and Cl- and may attach temporarily to the enzyme & change its site to make the shape more suitable for a reaction to take place”eg : a. calcium ion needed to activate thromokinase which converts prothrombin to thrombin in blood clottingb. chloride ions increase salivary amylase activity
- major reason for nutrional requirement for minerals is to supply such metal ions as Zn2+, Cu2+, K+ and Na+ for use in enzyme as cofactors
ENZYME INHIBITION
” a substanes that binds to an enzyme to decrease or stop the enzyme activity and may be reversible or irreversible”
- REVERSIBLE INHIBITION
- the inhibitor can be easily removed from the enzyme under certains conditions
- divide into 2
a. competitive inhibitors
b. non-competitive inhibitors
a. COMPETITIVE INHIBITORS
- reversible as the inhibitor binds temporarily to the active site and can be overcome by increasing the relative concentration of the substrate
- the inhibitor have a shape similar to the natural substrate and can fit temporarily into the active site of the enzyme
- the inhibitor and subsrate will compete for the same active site of the enzyme
- competition inhibition is reversed by increasing the substrate concentration
eg : a. malonate which compete with succinate for the active site on enzyme succinate dehydrogenaseb. CO poisoning which Co competes with O2 for active site on Hb. CO have higher affinity to the active sites of Hb hence O2 is displaced resulting the O2 deficiency and living tissue such as brain tissues will be destroyed even at very low CO concentration
b. NON-COMPETITIVE INHIBITOR
- have no structural similaritis to the substrate and doesnt attach to the active site but bind with the enzyme at another site (alosteric site)
- binding cause the change in conformation of the enzyme molecule and its active site so prevent the substrate from binding to the active site
- the inhibitor and substrate doesnt need to compete for the active site therefore the increase in substrate concentration doesnt affect the rate of reaction
eg : a. arsenic
b. cynide combine with metallic ions (acting as prosthetic group) of some enzyme and inhibits their activity
- IRREVERSIBLE INHIBITION
- the inhibitor bind very tightly and often forming covalent bond with the enzyme
- many pesticide such as organophosphate pesticide acts as irreversible enzyme inhibitors
- exposure to the pesticide can produce harmful effect to the nervous and muscular system of humans
eg : nerve gas and insecticide
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