Pr. Atkinson et al., PURIFICATION AND PRELIMINARY CHARACTERIZATION OF DDAP, A NOVEL DIPEPTIDYLAMINOPEPTIDASE FROM DICTYOSTELIUM-DISCOIDEUM, Biochemistry, 34(34), 1995, pp. 10827-10834
We have discovered and purified a novel dipeptidylaminopeptidase (DAP)
from the cell-free broth of Dictyostelium discoideum Ax3. The enzyme
is secreted in parallel with cell growth in axenic broth culture. It s
hares substrate preferences with both DAP-I and DAP-LII enzymes yet is
distinct from both in some physical properties. Similar to DAP-I, the
D. discoideum enzyme is able to cleave a variety of dipeptides from t
he amino termini of substrates. In addition, it readily cleaves substr
ate sequences beginning with RR- and KK-, a property of the DAP-m clas
s. The D. discoideum enzyme has a pH optimum of 3.5, a subunit molecul
ar mass of 66 000 daltons, and a molecular weight of approximately 225
000 and is not significantly inhibited by cysteine or serine protease
inhibitors. It is inhibited by leupeptin and trivalent cations. On th
e basis of enzymological and other data presented here, we conclude th
e D. discoideum enzyme does not belong to any of the previously report
ed DAP classes (DAP-I, -II, -III, -IV) and propose that the class DAP-
V be established with this D. discoideum enzyme as the first member.