Does mung bean nuclease cleave a phosphate group when it's chewing off 5' or 3' ssDNA ends? I'm looking to create blunt ends from sticky ends with mung bean nuclease for subsequent ligation. Does anyone know full mechanism by which mung bean nuclease will do this? In particular after the reaction, will the ends of resulting dsDNA have phosphate groups or will I need to phosphorylate the ends with an extra step for successful ligation?

According to Kroeker WD, Kowalski W, Laskowski M. 1976. Mung Bean Nuclease I. Terminally Directed Hydrolysis of Native DNA. Biochemistry 15(20):4463-4467

> It was concluded that the products of the terminally directed hydrolysis of native DNA possess 5’-phosphoryl groups because: (1) greater than 99% of acid-soluble activity applied to the column was recovered in products which coeluted with 5’-terminated standards and (2) the w-monophosphatase activity of mung bean nuclease would have dephosphorylated 3’-phosphoryl-terminated products. The endonucleolytic activity of mung bean nuclease on denatured DNA also results in the production of 5’-phosphoryl-terminated products.

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Also, from Promega:

> Mung Bean Nuclease catalyzes the degradation of single-stranded DNA and RNA endonucleolytically to yield 5´-phosphoryl-terminated products