Specific Effect of Salts in Extraction of Urease from Amoebocyte Tissue of Limulus.

Abstract

In a former communication 1 we have shown the presence of urease in the amoebocyte tissue, blood serum, muscle tissue and even in the unfertilized eggs of Limulus. In experiments carried out during the past summer we investigated means of extraction of this enzyme from experimental amoebocyte tissue, and we observed very striking differences in the extracting power of different salts.

Distilled water with or without the addition of urea is entirely or almost entirely ineffective. The Woods Hole sea water, which is alkaline, or sea water previously neutralized, heated blood serum of Limulus, or, serum from which the proteins have been removed through heating, show a very moderate degree of efficiency. Solutions of NaCl or KCl, approximately isotonic with sea water, behave in a similar manner to sea water, or are even slightly less effective than the latter. On the other hand, extracts prepared with isotonic solution of CaCl₂, BaCl₂ or SrCl₂ have a very high degree of activity. Solutions of MgCl₂ and also of MnCl₂ have an intermediate position, but approach more closely the former solutions than they do CaCl₂, SrCl₂ or BaCl₂. Solutions of CuCl₂ or ZnCl₂ are entirely or almost entirely without effect. Extracts made with isotonic solutions of CaCl₂, BaCl₂ or SrCl₂ are perhaps 40 to 100 times more active than extracts made with M/2 NaCl or M/2 KCl.

The anions tested thus far did not seem to possess a much greater extracting power than the corresponding chlorides. However, through increase in the concentration of various salts, we can increase their effectiveness. Thus the optimal concentration of NaCl seems to lie between 1.25 and 2.5 m, while in the case of CaCl₂ and also of MgCl₂ it seems to be approximately between 0.38 and 0.75 m.