Mung-bean nuclease 1 was first purified by Sung and Laskowski (1 ) in 1962 from mung-bean sprouts (Phaseolus aureus). It belongs to the class of enzymes EC 3.1.30.l., which has a preference for single-stranded nucleic acid substrates, lacks sugar specificity, and hydrolyzes single-stranded substrates to produce products with 5′-phosphoryl and 3′-hydroxyl termini, ranging from mono- to, at least, heptanucleotides. Although it shows a preference for single-stranded nucleic acids over double-stranded of 30,000-fold (2 ), used in high concentrations with extended incubation times, mung-bean nuclease 1 will completely degrade double-stranded DNA (3 –5 ). Mung-bean nuclease 1 is also reported to show a separate 3′-ω-monophosphatase activity (6 ) (seeSection 2.7. ). Mung-bean nuclease 1 is a zinc metalloenzyme that requires Zn2+ and a reducing agent, such as cysteine, for both activity and stability.
