Evidence for the chemical interaction of urease in solution

Abstract

2. The percentage of lecithin in the non-ruminant 'ghosts' was over three times as high as that found in ruminant 'ghosts'. 3. In contrast, the concentrations of sphingomyehn and choline plasmalogen were higher in ruminant 'ghosts' and consequently there were no significant differences between the concentrations of total choline-containing phospholipid in the various species. 4. Phosphatidylethanolamine was markedly higher in the 'ghosts' of omnivores than in 'ghosts' of herbivores. 5. Choline-containing phospholipids (mainly lecithin) accounted for over 94 % of the plasma phospholipid of all species. 6. Of the possible acidic phospholipids in erythrocyte 'ghosts' which could function as cation carriers, phosphatidylserine was present at a relatively high concentration (8-9-16 %) in all species, phosphatidylinositol varied from 1-6 % in man to 5-8 % in the goat and phosphatidic acid was below 1.5 % in all species. We are grateful to Mr F. Hills for valuable assistance.

Studies of the denaturation and partial renaturation of ovalbumin

“…After resolution of the peaks the sedimentation coefficients found were 3.3 and 4.4S. These values are consistent with those expected for the end-to-end dimerization of molecules of essentially native conformation (see, e.g., Creeth & Nichol, 1960). Only non-covalent interactions can be involved in the aggregation, because additional detergent dissociated the complex.…”

Arginine Synthesis, Proline Synthesis, and Related Processes

“…Sedimentation velocity investigations reveal six forms (S 2 o = 3, 12, 19, 28, 36, and 46 S) representing varying degrees of association (Bailey and Boulter, 1971). The predominant and presumably normal form, has a S 20 of 19 S and a molecular weight of about 480,000 (Creeth and Nichol, 1960). Bailey and Boulter (1969) demonstrated by Nand C-terminal examination that urease is composed of six identical subunits each with a molecular weight of 76,000 (an unusually large size).…”

A convenient method of preparation of high-activity urease from Canavalia ensiformis by covalent chromatography and an investigation of its thiol groups with 2,2'-dipyridyl disulphide as a thiol titrant and reactivity probe

“….'. These authors assumed that loss of the inessential thiol groups on storage is due to disulphide-bond formation, and some preparations of urease have been shown to contain aggregates containing intermolecular disulphide bonds (Creeth & Nichol, 1960). During this oxidation process, the reversal of the oxidation by treatment with 30mM-dithiothreitol at pH7.2 or pH9.3 for 30min became progressively less effective.…”