ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism...
-
Upload
malcolm-jenkins -
Category
Documents
-
view
213 -
download
0
Transcript of ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism...
![Page 1: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/1.jpg)
ENZYMES
![Page 2: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/2.jpg)
What are enzymes?
Biological catalysts Most are proteins Some RNA
Regulate metabolism
Respond to changing needs of cell
![Page 3: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/3.jpg)
All reactions require activation energy…
EA- needed to break existing bonds Even exergonic reactions require EA http://www.indiana.edu/~oso/animations/fire.html
Enzymes lower EA
Allow reactions to occur more quickly No effect on free-energy change http://www.stolaf.edu/people/giannini/flashanimat/enzymes/transition
%20state.swf
Enzymes reduce reliance on random collision of reactants
http://www.stolaf.edu/people/giannini/flashanimat/enzymes/prox-orien.swf
![Page 4: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/4.jpg)
![Page 5: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/5.jpg)
Enzyme-Substrate Complex
Every enzymes contains 1 or more active sites
Substrate binds – forms enzyme-substrate complex
Enzyme changes shape slightly – induced fit
http://www.stolaf.edu/people/giannini/flashanimat/enzymes/enzyme.swf
![Page 6: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/6.jpg)
Shape of substrate may change also – straining existing bonds
Products form, diffuse away
Enzyme can be used again – is not used up in the reaction
![Page 7: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/7.jpg)
Specificity of Enzymes
Most are highly specific due to shape of active site
May catalyze: Few closely related reactions Many only catalyze one reaction
![Page 8: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/8.jpg)
Cofactors Some enzymes have 2 components
Apoenzyme – protein Cofactor – additional component Alone, neither is catalytic
Cofactors may be Inorganic – Ca, Mg, trace elements Coenzymes – organic, nonpeptide
Carrier molecules ATP Vitamins
![Page 9: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/9.jpg)
Enzymes work best under specific conditions
Temperature In humans, most 35oC - 40oC Low temps –slow or not at all due to
molecular motion High temps – increase to a point;
denature
![Page 10: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/10.jpg)
pH Humans, 6-8 Some, ex. stomach enzymes, work in
low pH Buffers – impt to minimize pH changes
Change in pH alters electric charges in R-groups of enzymes denature
![Page 11: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/11.jpg)
Metabolic Pathways
Series of enzyme-catalyzed reactions
Enzymes aid in reaction coupling
Work in sequence Product of 1 enzyme, the reactant in
next
A enzyme 1> B enzyme 2> C
![Page 12: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/12.jpg)
Each reaction is reversible, but Intermediate and
final products are removed
Drives the sequence of reactions to the right
![Page 13: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/13.jpg)
Regulation of Enzyme Activity
Enzyme or Substrate Concentration
Feedback InhibitionAllosteric Enzymes
![Page 14: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/14.jpg)
Regulation of Enzyme Activity
Synthesis of enzyme Gene turned on/off by signal
Substrate concentration If excess substrate, enzyme conc. is
limiting factor Low conc. of substrate can be rate-
limiting factor also
![Page 15: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/15.jpg)
![Page 16: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/16.jpg)
![Page 17: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/17.jpg)
Feedback Inhibition Product of one enzymatic reaction
controls the activity of another
If product later in pathway inhibits an enzyme earlier in reaction sequence = feedback inhibition
Aenzyme 1>B enzyme 2>C enzyme 3>D enzyme 4>E
![Page 18: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/18.jpg)
Allosteric Enzymes Exist in active and inactive forms Inactive form – active site doesn’t
allow substrate to bind http://www.stolaf.edu/people/giannini/flashanimat/enzymes/allosteric.swf
Allosteric site – receptor site, other than active site, which binds regulators and alters active site Inhibitors Activators
![Page 19: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/19.jpg)
Effects of chemical agents:
Can destroy or inhibit enzymes Inhibition can be irreversible
Permanently inactivates enzyme Combines with active site, allosteric
site Ex. Mercury, lead, cyanide
Reversible inhibition – weak chemical bonds Competitive or noncompetitive
![Page 20: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/20.jpg)
Competitive inhibition
Inhibitor competes with substrate for active site Structurally similar but cannot
substitute for substrate Temporarily occupies active site
Concentration matters
![Page 21: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/21.jpg)
Noncompetitive Inhibition
Competitor binds to site other than active site alters shape
Useful in feedback inhibition
Allosteric inhibition is an example
![Page 22: ENZYMES. What are enzymes? Biological catalysts Most are proteins Some RNA Regulate metabolism Respond to changing needs of cell.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2d32f/html5/thumbnails/22.jpg)