Histaminase and its inhibitory factor in guinea pig skin.

The crude histaminase preparation obtained from guinea pig skin was fractionated by Sephadex G-200 at 4°C and 55°C. The histaminase activity corresponded to the descending limb of the :first peak of protein eluted just after void volume at 4°C and to the second peak at 55°C. The histaminase activity in the fractions eluted at 4°C was higher at 55°C than at 37°C. On the contrary, no significant difference between the histaminase activity assayed at 55°C and 37°C was observed in the fractions eluted at 55° C; On Sephadex G-200 gel filtration, histaminase was eluted in the later fractions at 55°C, compared with the fractions eluted at 4°C, indicating that the molecular weight of histaminase may become smaller at 55° C. These facts suggest that histaminase obtained from guniea pig skin may bind with an inhibitor-like substance at low temperature and that the enzyme may separate from the inhibitor at high temperature.