Methods in Molecular Biology • 16 Enzymes of Molecular Biology

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CHAPTER 12

Mung-Bean Nuclease I (EC 3.1.30.1)


Andrew J. Sharp and Robert J. Slater



  1. Introduction
    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 3.1.30.1., which has a preference for single-
    stranded nucleic acid substrates, lacks sugar specificity, and hydro-
    lyzes single-stranded substrates to produce products with 5'-phosphoryl
    and 3'-hydroxyl termini, ranging from mono- to, at least, heptanucleo-
    tides. 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'-to-monophosphatase activity (6) (see Sec-
    tion 2.7.). Mung-bean nuclease 1 is a zinc metalloenzyme that requires
    Zn 2+ and a reducing agent, such as cysteine, for both activity and stability.
    Mung-bean nuclease 1 has been used in the removal of protruding
    tails in double-stranded DNA, in the excising of cloned DNA frag-
    ments inserted into vectors, and in other techniques we describe later
    in this chapter. We also discuss some of the background enzyme data
    for those wishing to understand the enzyme in more detail and for
    those wishing to modify standard protocols to suit their own purposes.
    Although it is not within the scope of this chapter to try to cover all of
    the available data regarding specificity and mechanism of cleavage,
    the information provided here should be adequate for most workers
    seeking a general understanding.


From: Methods in Molecular Biology, Vol. 16: Enzymes of Molecular Biology
Edited by: M. M. Burrell Copyright ©1993 Humana Press Inc., Totowa, NJ

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