Chapter 3 - Enzymes - activity determination Flashcards
What does Oxidoreductases catalyze?
They catalyze reactions of oxidation and reduction
Which 4 groups are Oxidoreductases classified into?
- oxidases
- dehydrogenases
- hydroperoxidases
- oxygenases
What does oxidases do?
They transfer hydrogen from a substrate to oxygen
What does dehydrogenases do?
They transfer hydrogen from one substrate to another (not oxygen); they require coenzymes/prosthetic groups such as NAD, ADP, FAD, FMN.
What does hydroperoxidases do?
They use hydrogen peroxide or organic peroxides for oxidation of differen substrates.
What does oxygenases do?
They incorporate oxygen into a substrate.
Peroxidase = ?
Hydroperoxidases
Which enzymes use hydrogen peroxide to oxidize different substances (peroxidase actvity)?
- catalase
- peroxidase (hydrogenperoxidase)
Where is catalase found?
- blood
- liver
- kidney
Where is peroxidase found?
- plants
- leucocytes
- milk
Catalase uses ______ _______ as an electron acceptor.
Hydrogen peroxidase
Which color does oxidized benzidin have?
Intensive blue color
Give an example of a copper containing enzyme:
o-Diphenol oxidase
Where are o-Diphenol oxidase present?
They are present in plants
What does o-Diphenol oxidase do?
o-Diphenol oxidase transfer hydrogen from a substrate to molecular oxygen forming water
What does the Cytochrome oxidase do?
Cytochrome oxidase catalyzes the final step of the electron transport chain (respiratory chain); the transfer of electrons from cytochromes c to oxygen.
What does the cytochrome contain?
It contains two molecules of heme, and two ions of copper
What reduces cytochrome c?
P-phenyldiamine
Succinate dehydrogenase:
- is a compinent of the electron transport chain (respiratory chain) and the tricarboxylic acid cycle ( TCA, Krebs cycle)
- is bound to inner mitochondrial membrane
- contains; FAD and iron sulfur (Fe-S) centres as prosthetic group
- Malonate (HOOC-CH2-COOH), succinate analogue, is a very strong competitive inhibitor of this enzyme
What is the third class of enzymes (EC 3) called;
Hydrolases
What does Hydrolases do?
They hydrolyze different types of chemical bounds such as;
- peptide bonds (peptidase, e.g pepsin, trypsin, chymotrypsin, carboxy-peptidase, aminopeptidase)
- glycosdidic bonds (glycosidases, e.g. amylase, maltase, sucrase)
- ester bonds (esterases, e.g lipase, phosphatase.
Arginase
Is a hydrolase which catalyzes the last reaction of the urea cycle in the liver.
Is urease present in humans?
No
Where is urease present?
In many plants and microorganisms
