An extracellular esterase from the actinomycetes Amycolatopsis Orientalis was found by screening. It is capable of splitting the isomeric mixture (K/J) of (I, Scheme 1) into 7-amino-3-methoxymethyl-3-cephem-4-carboxylic acid, pivalic acid, and acetaldehyde with a high yield.(1) The purified enzyme of 55.4 Kd by SDS-PAGE shows an N-terminal sequence of VRTCADLVRTYDLPGAVTH. The isoeletric point is 8.9 +/- 0.1. It can be immobilized with good yield to VA-Epoxy Biosynth(R). Besides the above-mentioned reaction, the esterase cleaves many other esters such as methyl-2-chloropropionic acid.