The ability of a rat lens homogenate to degrade radioiodinated zinc insulin into fractions which now are TCA soluble was used as a criterion of proteolysis. The assay method is extremely simple, rapid, and sensitive. Proteolytic activity is linearly related to the amount of lens homogenate added. The lens enzyme has a pH optimum of approximately 7.2, a temperature maximum near 50° C, and is ina...

An enzyme which promotes the degradation of insulin has been isolated from beef liver (2, 3). This enzyme, which has been designated glutathione-insulin transhydrogenase (4), catalyzes the reductive cleavage of the disulfide bonds of insulin by a simple sulfhydryl compound such as glut,athione (4, 5). Because the process of degradation may be important in the etiology of diabetes mellitus, expe...

The relationship between the state of oligomerization and activity of purified maize leaf phosphoenolpyruvate carboxylase using size exclusion high performance liquid chromatography was examined. Maximum activities of 35 to 38 micromoles per minute per milligram protein were found when 100% of the enzyme was in its tetrameric form. The effects of the sulfhydryl group modifiers CuCl(2) and p-chl...

The influence of Mg2+ ions and temperature on the structure of the enzyme ribulose-1,5-bisphosphate carboxylase was investigated using the fluorescent probe 1-anilino-8-naphthalene sulfonate (ANS). The binding of ANS to the enzyme molecule caused a significant increase of fluorescence emission which was further enhanced by the addition of Mg2+. The temperature dependence of the fluorescence emi...

The sodiumand potassium-activated adenosine triphosphatase (Naf + K+)-ATPase was partially purified from a microsomal fraction of whole rabbit brain, homogenized in a deoxycholate buffer. Suspension and separation by flotation of the resulting lipoproteins in a linear gradient of potassium iodide formed the basis of a rapid preparative technique, whereby the enzyme-containing lipoproteins were ...

Digitonin-permeabilized neutrophils were exposed to micromolar levels of a variety of heavy metal cations and sulfhydryl oxidants to gain insight into the potential biochemical mechanisms underlying neutrophil degranulation. The results from this study suggest that the oxidation of intracellular sulfhydryl groups may play a role in neutrophil signal transduction. Evidence to support this conclu...

The influence of alcohols with different alkyl chain length (methanol, ethanol and propanol) on the physicochemical properties (turbidity, surface hydrophobicity, exposed total free sulfhydryl ...

The mimivirus genome contains many genes that lack homologs in the sequence database and are thus known as ORFans. In addition, mimivirus genes that encode proteins belonging to known fold families are in some cases fused to domain-sized segments that cannot be classified. One such ORFan region is present in the mimivirus enzyme R596, a member of the Erv family of sulfhydryl oxidases. We determ...

The interaction of acrylamide with rabbit muscle glyceraldehyde-3-phosphate dehydrogenase (GPDH) has been investigated in Tris buffer, pH 7.5. When GPDH containing about 1 mol NAD per mol of tetramer is incubated with acrylamide (0.01-0.1 M), the tryptophan emission of GPDH, initially quenched by acrylamide, slowly increases to a value exceeding that recorded before the addition of acrylamide. ...

A calcium (Ca2+)-activated, neutral proteinase has been purified from Ehrlich ascites tumor cells. The protocol used has resulted in a 3,600-fold purification of the enzyme in a yield of 21% from the Ehrlich ascites tumor cell postnuclear supernatant. The purified proteinase has a high substrate specificity for the intermediate filament subunit proteins, vimentin and desmin, and showed no activ...