• reactants must collide with each other
• reactants must collide in right orientation
• reactants must collide with sufficient energy

Two imporant factors which alter rate of reaction

temperature

catalyst

• temp. increase leads to increase rate
  • for every 10 degrees, rate doubles
• increases Brownian mov't (increase molecule movement)

• will increase rate of reaction
• provides surface upon which reactants can bind in the correct orientation
  • leads to lowering activation energy
  • one molecule of catalyst can convert many molecules of reactant to product

amount of energy that is available to do work (difference between energy of products and reactants)

NO EFFECT (just helps it reach equilibrium faster)

• oxidoreductase
• transferase
• hydrolyase
• lyase
• isomerase
• ligase

• Function- catalyze oxidation reduction rxn
• examples
  • dehydrogenases
  • monooxygenases
  • dioxygenases
  • reductases

• function- catalyze transfer of a group from one molecule to another
• example
  • aminotransferase
  • methyltransferase
  • kinase

Function and example of hydrolyase

• function- hydroyxix rxn
• examples
  • phosphatases
  • lipases
  • peptidases

• function- catalyze removal of double bond
• example
  • fumarate
  • argininosuccinase

• function- isomerization rxns
• examples
  • hexose isomerase

• function- formation of bond using ATP
• example
  • Gln synthetase
  • DNA lyase

Describe AA's in active site of chymotrypsin and how it catalyzes the hydrolysis of peptide bond

• peptide bond of aromatic AA with is carboxyl side chain lines up next to three AA's
  • OH of Ser
  • imidazole ring of His
  • carboxyl group of Asp
• OH of Ser will catalyze hydrolysis of peptide bond on carboxyl side of aromatic AA

1. aromatic AA bind into pocket
2. enzyme folds to bring Ser, His, Asp close together
3. hydrogen from OH on Ser attacks N on imidazole ring of His
4. leads to attack of H on N in His on beta carboxyl group in Asp
5. oxygen free radical remaining on Ser attacks carbonyl group on peptide bond, leadin to its hydrolysis

1. inorganic (some kind of ion to stabilize confirmation or participate in rxn)
2. organic (called coenzyme)
   1. carrier
   2. prosthetic

apoenzyme

coenzyme

• contains Cys and His
• H on SH group of Cys involved in H attack on His N

Mechanism of action of coenzyme

• it is a part of active site
• binds to and moves "mobile group" (some chemical group) from substrate to acceptor
• these are two step reactions

• first rxn- at active site, mobile group removed from substrate by coenzyme
  • forming coenzyme-X complex
  • forms product
• second rxn- coenzyme-X complex pass mobile group acceptor
  • forms acceptor-X
  • regenerates coenzyme

• leaves the active site
• than carries mobile group to another enzymes active site where it passes group to acceptor molecule

• NAD
• NADP

Where NAD and NADP function and the mobile group of the reaction

• function at active site of dehydrogenaes
• mobile group- hydride ion

Importance of NAD and NADH not being able to cross into mitochondrial matrix or into cytosol

• each compartment has a pool of NAD or NADH
• concentration of NAD and NADH combined in each compartment will not be changed
• the relative conc. of each form may change, but the total conc. of both combined will not change

1. via reduction of NAD, form acetaldehyde from ethanol
2. via oxidation of NADH, form lactic acid from pyruvic acid

Mobile group of tetrahydrofolate

CoA

acyl carrier protein (ACP)

Coenzyme of niacin

NAD

NADP

FMN

FAD

methyl-B12

5' adenosyl B12