Aminopeptidase activity associated with purified murine leukaemia viruses.

Rauscher leukaemia virus (RLV), extensively purified by rate and density gradient centrifugation procedures, exhibited aminopeptidase (AP) activity. The amount of virion activity was about 0.005 times the specific activity of purified hog kidney aminopeptidase M (EC 3.4.11.2). The activity was also found in purified Moloney and Gross leukaemia viruses, but not in comparable gradient fractions of uninfected JLSV-9 cells. Furthermore replacement of serum by bovine serum albumin in the growth medium of virus producing cells did not affect the AP activity. These results indicate that murine leukaemia viruses (MuLV) possess a tightly bound AP activity which is present as a minor component of the virion preparation and is probably not due to host cell membrane or serum contamination. Characterization of the pH optimum and substrate specificity show the MuLV aminopeptidase activity is similar to but different from both hog kidney, leucine aminopeptidase (EC 3.4.11.1) and aminopeptidase M (EC 3.4.11.2).