The association of K(+)-stimulated, Mg(2+)-dependent ATPase activity with plasma membranes from higher plants has been used as a marker for the isolation and purification of a plasma membrane-enriched fraction from cauliflower (Brassica oleraceae L.) buds. Plasma membranes were isolated by differential centrifugation followed by density gradient centrifugation of the microsomal fraction. The de...

An optimal environment for glucose oxidase (GOx) in Nafion membranes is achieved using an advanced immobilization protocol based on a nonaqueous immobilization route. Exposure of glucose oxidase to water-organic mixtures with a high (85-95%) content of the organic solvent resulted in stabilization of the enzyme by a membrane-forming polyelectrolyte. Such an optimal environment leads to the high...

During the course of a study of glycoprotein processing mannosidases in the rat epididymis, we have made an intriguing discovery regarding the presence of a novel alpha-D-mannosidase on the rat sperm plasma membranes. Unlike the sperm acrosomal "acid" mannosidase which has a pH optimum of 4.4, the newly discovered alpha-D-mannosidase has a pH optimum of 6.2, and 6.5 when assayed in sperm plasma...

Incubation of a hepatocyte particulate fraction with ATP and the isolated catalytic unit of cyclic AMP-dependent protein kinase (A-kinase) selectively activated the high-affinity 'dense-vesicle' cycle AMP phosphodiesterase. Such activation only occurred if the membranes had been pre-treated with Mg2+. Mg2+ pre-treatment appeared to function by stimulating endogenous phosphatases and did not aff...

CPT (carnitine palmitoyltransferase) 1 and CPT2 regulate fatty acid oxidation. Recombinant rat CPT2 was isolated from the soluble fractions of bacterial extracts and expressed in Escherichia coli. The acyl-CoA chain-length-specificity of the recombinant CPT2 was identical with that of the purified enzyme from rat liver mitochondrial inner membranes. The Km for carnitine for both the mitochondri...

Extravasation of peripheral blood monocytes through vascular basement membranes requires degradation of extracellular matrix components including heparan sulfate proteoglycans (HSPGs). Heparanase, the heparan sulfate-specific endo-beta-glucuronidase, has previously been shown to be a key enzyme in melanoma invasion, yet its involvement in monocyte extravasation has not been elucidated. We exami...

Sterol-induced binding to Insigs in endoplasmic reticulum (ER) membranes triggers ubiquitination of the cholesterol biosynthetic enzyme 3-hydroxy-3-methylglutaryl CoA reductase. This ubiquitination, which is mediated by Insig-associated ubiquitin ligases gp78 and Trc8, is obligatory for extraction of reductase from lipid droplet-associated ER membranes into the cytosol for proteasome-mediated, ...

Guanylate cyclase is regulated by adenine nucleotides in membranes of intestinal mucosal cells. Basal guanylate cyclase was activated about twofold by adenine nucleotides. Activation was specific for adenine, as compared with the pyrimidine nucleotides UTP and CTP. In addition, enzyme activation was obtained in the presence of saturating concentrations of GTP, the substrate for guanylate cyclas...

Plasma membrane fractions I and II isolated from bovine corpus luteum contain phosphoprotein phosphatases. Enzyme activities associated with both membrane fractions showed pH optima in the neutral range and were most active with phosphoprotamine as the exogenous substrate. The enzyme activity was partially inhibited by Co2+, Zn2+ and Fe2+. Dithioerythritol, glutathione (reduced) and 2-mercaptoe...

A highly effective method was developed to functionalize ceramic supports (Al2O3 powders and membranes) using newly synthesized spacer molecules. The functionalized materials were subsequently utilized for Candida antarctica lipase B enzyme immobilization. objective is systematically evaluate the impact of various molecules grafted onto alumina will affect both immobilization enzymes specific m...