The Specific Action of Salts in Preparation of Urease from Amoebocyte Tissue of Limulus.

Abstract

In previous investigations Loeb and Bodansky 1 found that different salts have a specific action in the extraction of urease from amoebocyte tissue of Limulus, in accordance with the character of the kations. The salts of alkaline earths are by far the most favorable; the salts of alkali metals are very unfavorable, and the salts of Mg and in decreasing order Mn are intermediate in effectiveness. While extracts prepared with salts of heavy metals are apparently of similar strength to those prepared with salts of alkali metals, the addition of the salts of heavy metals to active extracts is very much more injurious than the addition of salts of alkali metals.

We recently analyzed the effect of mixtures of salts in the preparation of the urease, and the effect of addition of salts after the extraction with certain salts had been completed. If mixtures of salts are used in the preparation of extracts, the activity of the extracts thus prepared is approximately intermediate between the activity that is characteristic of each component salt; this applies to various combinations of NaCl, MgCl₂ and CaCl₂. If on the other hand, the extraction is first completed and then another salt is added, the results vary in accordance with the salt used for extraction. If we extract with NaCl and add a more favorable salt to the extract the addition of the latter salt is ineffective. On the other hand, if the extract has been prepared with MgC1₂, the subsequent addition of CaC1₂, leads to a condition in which the activity coefficient is intermediate between the activity coefficient of MgC1₂, extract and the activity coefficient of CaCl₂, extract.

While extraction with Limulus serum in which the preformed urease has been previously inactivated through heating to 80° for 30 minutes, is more favorable than extraction with 0.5 m. NaCl SOlution, only a slight improvement in the activity of this extract can be produced through addition of CaC1₂, at the beginning of the extraction, and the effect is injurious if CaC1₂, is added to the extract.