Ligase enzymes

Ligases. Enzymes that catalyse the formation of bonds and require ATP. 

S. Except for oxido-reductases, transferases, and hydrolases, most ligases (enzymes that catalyze bond formation) are entirely substrate specific. Thus, fumarate hydratase (or fumarase) reversibly and stereospecifically adds water to fumaric acid to produce (S)-( — )-malic acid only (8) (Figure 1), and another enzyme, mesaconase, adds water to mesaconic acid to form (+ )-citramalic acid (9) (Figure 2). Although no extensive studies are available, it appears that neither fumarase nor mesaconase will add water stereospecifically to any other a,(3-unsaturated acid. 

Ligases Enzymes that initiate the linkage of two segments of DNA. 

T4-DNA kinase. Enzyme isolated from phage T4 infected E. coli which catalyses the transfer of the y-phosphate group of rATP to the 5 -hydroxyl terminus of DNA and RNA T4-DNA ligase. Enzyme isolated from phage T4 infected E. coli which catalyses its formation of a phosphodiester bond between adjacent 5 -phosphorylated and 3 -hydroxy terminated DNA strands... 

Recall What are the functions of the gyrase, primase, and ligase enzymes in DNA replication ... 

---