Biotechnology Homework Help: Classification of Enzymes
Enzymes and classified and named by the commission on Biochemical Nomenclature of the International Union of Biochemistry. An enzyme may be denoted in one of the following 3 accepted ways: (i) a four number code following the letters EC (for Enzyme Commission), e.g. EC 188.8.131.52 (the first number refers to enzyme class, the second to subclass, the third to sub-subclass and the fourth to the serial number of the enzyme within a sub-subclass), (ii) its systematic name based on the above and (iii) its recommended name. According to home work helper the enzymes have been classified in the following 6 classes.
1. Oxidoreductases are involved in redox reactions, i.e. transfer of hydrogen or oxygen atoms between molecules. This class includes: dehydrogenases (hydride transfer), oxidases (e- transfer to O2), oxygenases (oxygen atom transfer from O2), and peroxidases (e- transfer to peroxides). Example, glucose oxidase (EC 184.108.40.206).
2. Hydrolases are those enzymes which catalyze hydrolytic reactions (and group of atoms from the substrate molecule. This class includes aldolases, decarboxylases, dehydratases and some pectinases. Example, histidine ammonia lysae (EC 220.127.116.11).
3. Lyases are involved in elimination reactions resulting in the removal of a group of atoms from the substrate molecule. This class includes aldolases, decarboxylases, dehydratases and some pectinases. Example, according to studydaddy histidine ammonia lysae (EC 18.104.22.168).
4. Isomerases catalyse the formation of isomers of molecules; they include epimerases, racemases and intramoelcular transferases. Example, xylose isomerase (EC 22.214.171.124).
5. Ligases or Synthetases catalyze the formation of covalent bonds between two molecules utilizing the energy obtained from hydrolysis of a nucleoside triphosphate like ATP, GTP. Example, glutathione synthase (EC 126.96.36.199).
Coli Vectors and Plasmids
Bacteria are the hosts of choice for DNA cloning. Among then, E. coli occupies a prominent position since cloning and isolating DNA inserts for structural analysis is the easiest in this host. Therefore, the initial cloning experiments are generally carried out in the E. coli. The E. coli strain K12 is the most commonly used; it has several substrains, e.g. C 600, RRI, HB 101 etc. each of which has some specific features important in cloning. For example, according to studydaddy the substrain RRI has, in addition to certain other features, the mutation hsdR which inactivates the restriction enzyme endogeneous to E. coli K 12; this degradation of recombinant DNA introduced into it.