Structural Biochemistry/Enzymes Used in Molecular Biology

1. Type II restriction endonucleases: Enzymes cleave DNA at specific sequences to form DNA fragments. It cuts double stranded DNA at a specific base sequences. In prokaryote, enzyme is used to cleave foreign DNA molecules.

2. DNA ligase DNA ligase is an enzyme that joins two DNA molecules or fragments together They are used in cloning where the recombination DNA molecules occur. The DNA ligase can also be used in DNA replication.

3. DNA polymerase I DNA polymerase I (E.Coli) is an enzyme that fills gaps in duplexes by stepwise addition of nucleotides to 3'-ends for DNA sequence. DNA polymerase I is an important enzyme to be used in DNA sequencing, DNA replication, and PCR. It is used to insert the right nucleotides into a primer to start base-pairings.

4. Reverse Transcriptase Reverse Transcriptase is an enzyme to make a DNA copy of an RNA molecule. It is used in retrovirus reaction where genetic information flows from RNA to DNA. Retrovirus Reaction: single stranded RNA --(reverse transcriptase to synthesize RNA to DNA)--> double stranded DNA-RNA hybrid --(reverse transcriptase is used again to degrade RNA)--> single stranded DNA transcript --(reverse transcriptase to synthesize the second strand of DNA)--> double stranded DNA

5. Polynucleotide Kinase Polynucleotide kinase is added to a phosphate to the 5’-OH end to label or permit DNA/RNA in a ligation.

6. Exonuclease III Exonuclease III is an enzyme that removes nucleotide residues from 3’-end of DNA strand.

7. Alkaline Phosphate: Alkaline Phosphate is used to remove phosphates terminal.