Mung bean nuclease (Nuclease MB) is a nuclease derived from sprouts of the mung bean (Vigna radiata) that removes nucleotides in a step-wise manner from single-stranded DNA molecules (ssDNA) and is used in biotechnological applications to remove such ssDNA from a mixture also containing double-stranded DNA (dsDNA). This enzyme is useful for transcript mapping, removal of single-stranded regions in DNA hybrids or single-stranded overhangs produced by restriction enzymes, etc. It has an activity similar to Nuclease S1 (both are EC 3.1.30.1), but it has higher specificity for single-stranded molecules.

The enzyme degrades single-stranded DNA or RNA to nucleoside 5’-monophosphates, but does not digest double-stranded DNA, double-stranded RNA, or DNA / RNA hybrids. Mung Bean Nuclease catalyzes the specific degradation of single-stranded DNA or RNA, and produces mono and oligonucleotides carrying a 5′-P terminus. Mung bean nuclease has a stringent single-stranded specificity for DNA or RNA.

Mung bean nuclease has an estimated molecular weight of 39 kDa by SDS-PAGE. A glycoprotein, 29% of this mass is sugars. As of April 2019, the specific gene encoding for this protein is unknown, and all production relies on a purification process on bean sprouts from 1980. Some is known about its structure, with one exposed Cysteine residue and 3 pairs of disulfide bonds. Some is known about its amino acid composition.