Human cerebrospinal fluid has been found to mimic the effect of ouabain on net Na+ efflux and 86Rb+ influx across erythrocyte membranes and on the in vitro activity of a purified Na+/K+-ATPase (ATP phosphohydrolase, EC 3.6.1.3) derived from canine kidney. These results indicate the possible existence in human cerebrospinal fluid of an endogenous factor with ouabain-like activity, which might be...

Alkaline phosphatase [orthophosphoricmonoester phosphohydrolase (alkaline pH optimum), EC 3.1.3.1] purified from a Burkitt lymphoma cell line (Daudi) and Moloney-virus-induced murine leukemia (YAC) showed unique catalytic properties in substrate specificity and inhibition by cysteamine-S-phosphate. It migrated on polyacrylamide gel electrophoresis in a single activity band. Alkaline phosphatase...

The whole nucleotide sequence of Escherichia coli gene appA, which encodes periplasmic phosphoanhydride phosphohydrolase (optimum pH, 2.5), and its flanking regions was determined. The AppA protein is significantly homologous to the product of the nearby gene agp, acid glucose-1-phosphatase. Because identical amino acids are distributed over the whole lengths of the proteins, it is likely that ...

The diphosphoinositol polyphosphates ("inositol pyrophosphates") are a specialized subgroup of the inositol phosphate signaling family. This review proposes that many of the current data concerning the metabolic turnover and biological effects of the diphosphoinositol polyphosphates are linked by a common theme: these polyphosphates act as metabolic messengers. This review will also discuss the...

Ectonucleotidase proteins occupy a central role in purine signalling regulation by sequentially hydrolysing ATP to ADP and to adenosine. The ENPP ( or PDNP) gene family, which encodes ectophosphodiesterase/nucleotide phosphohydrolases, is a subfamily of these enzymes, which consists of 7 members in mammals. These proteins catalyse the generation of bioactive lipids, placing the ENPP enzymes as ...

The specific enzymatic activity of pyrophosphate phosphohydrolase in the soluble fraction from C3HBA mammary adenocarcinoma of mice varies with age of the tumor. Removal of Ca++ by addition of ethylenediaminetetraacetic acid to the incubation medium greatly enhanced activity of the enzyme. The pattern of variation (increase during the 1st 14-16 days post transplant followed by rapid diminution ...

The lung contains two distinct forms of phosphatidic acid phosphatase (PAP). PAP1 is a cytosolic enzyme that is activated through fatty acid-induced translocation to the endoplasmic reticulum, where it converts phosphatidic acid (PA) to diacylglycerol (DAG) for the biosynthesis of phospholipids and neutral lipids. PAP1 is Mg(2+) dependent and sulfhydryl reagent sensitive. PAP2 is a six-transmem...

Ras-transformation of cells is accompanied by an increase of the level of diacylglycerol (DAG), which participates in the signal transduction pathways. DAG could be generated from phospholipids either by activation of phospholipase C or by a more complex pathway involving phospholipase D and phosphatidate phosphohydrolase. To clarify which phospholipids produce DAG and which pathways are involv...

SAMHD1 (SAM domain- and HD domain-containing protein 1) is a dGTP-dependent dNTP triphosphohydrolase that converts dNTPs into deoxyribonucleosides and triphosphates. Therefore, SAMHD1 expression, particularly in non-dividing cells, can restrict retroviral infections such as HIV and simian immunodeficiency virus by limiting cellular dNTPs, which are essential for reverse transcription. It has pr...

The human neuroblastoma cell line SK-N-SH comprises cells that undergo morphological and biochemical interconversion between a primitive sympathoblast and a variant, epithelial-like cell type which does not express the neuronal characteristics of the SK-N-SH cell line. Since neural crest cells, from which neuroblastomas are presumed to arise, can undergo transdifferentiation in culture from a n...