Ribonucleases from T2 family.

Ribonucleases are ubiquitous in distribution. Ribonucleases that hydrolyse RNA to 3' mononucleotides via 2', 3' cyclic nucleotides are classified into three groups, RNase A, RNase T1, and RNase T2 families. Apart from salvage of cellular or extracellular RNAs, RNases participate in vital cellular functions such as DNA replication, transcription and RNA processing, splicing and editing, and control of translation by determining the turnover of RNA. T2 family RNases have been implicated in nutrition, phosphate remobilization, self-incompatibility, senescence, and defense against pathogens. They are important analytical enzymes and have been exploited for the structural determination of RNAs. Although considerable information is available on RNase A and T1 family RNases, less information is available on RNases from T2 family except RNase Rh from Rhizopus niveus and RNase LE from tomato. However, during the last few years, the primary structure, active site nature based on sequence homology, and probable mechanism of action have been postulated for some of these enzymes. RNases of T2 family, their occurrence, purification, characteristics, biological role, and applications have been reviewed.