Search results for "Exopolyphosphatase"
showing 6 items of 6 documents
Changes in metabolism of inorganic polyphosphate in rat tissues and human cells during development and apoptosis
1997
Age-dependent studies show that the amount of inorganic polyphosphate in rat brain strongly increases after birth. Maximal levels were found in 12-months old animals. Thereafter, the concentration of total polyphosphate decreases to about 50%. This decrease in the concentration of total polyphosphate is due to a decrease in the amount of insoluble, long-chain polyphosphates. The amount of soluble, long-chain polyphosphates does not change significantly in the course of ageing. In rat embryos and newborns, mainly soluble polyphosphates could be detected. In rat liver, the age-dependent changes are less pronounced. The changes in polyphosphate level are accompanied by changes in exopolyphosph…
Purification and characterization of two exopolyphosphatases from the marine sponge Tethya lyncurium
1995
Abstract Two exopolyphosphatases (exopolyphosphatase I and II; EC 3.6.1.11) which release orthophosphate from inorganic polyphosphates have been detected and purified for the first time from a marine sponge, Tethya lyncurium . Exopolyphosphatase I has a molecular mass of 45 kDa, a pH optimum of 5.0 and does not require divalent cations for activity, while exopolyphosphatase II has a molecular mass of 70 kDa, a pH optimum of 7.5 and displays optimal activity in the presence of Mg 2+ ions. Final purification of the enzymes could be achieved by affinity chromatography on polyphosphate-modified zirconia. The mode of action of both enzymes was found to be processive. Orthophosphate is the sole p…
Mammalian intestinal alkaline phosphatase acts as highly active exopolyphosphatase.
2001
Recent results revealed that inorganic polyphosphates (polyP), being energy-rich linear polymers of orthophosphate residues known from bacteria and yeast, also exist in higher eukaryotes. However, the enzymatic basis of their metabolism especially in mammalian cells is still uncertain. Here we demonstrate for the first time that alkaline phosphatase from calf intestine (CIAP) is able to cleave polyP molecules up to a chain length of about 800. The enzyme acts as an exopolyphosphatase degrading polyP in a processive manner. The pH optimum is in the alkaline range. Divalent cations are not required for catalytic activity but inhibit the degradation of polyP. The rate of hydrolysis of short-ch…
Inorganic Polyphosphate in Human Osteoblast-like Cells
1998
Significant amounts of inorganic polyphosphates and of polyphosphate-degrading exopolyphosphatase activity were detected in human mandibular-derived osteoblast-like cells. The amount of both soluble and insoluble long-chain polyphosphate in unstimulated osteoblast-like cells was higher than in human gingival cells, erythrocytes, peripheral blood mononuclear cells, and human blood plasma. The cellular content of polyphosphate in osteoblast-like cells strongly decreased after a combined treatment of the cells with the stimulators of osteoblast proliferation and differentiation, dexamethasone, beta-glycerophosphate, epidermal growth factor, and ascorbic acid. The amount of soluble long-chain p…
Inorganic polyphosphates in the developing freshwater spongeEphydatia muelleri: Effect of stress by polluted waters
1996
Relatively high amounts of inorganic polyphosphates (approximately 55 μg of polyphosphate/g of wet weight) were found in the freshwater sponge Ephydatia muelleri, particularly in the gemmules (260 μg/g). Here we report that the polyphosphate content of this sponge changes during development and in response to adverse environmental conditions. Germination and hatching of gemmules of E. muelleri is accompanied by a strong decrease (by 94% at day 2) in polyphosphate level and a rise in exopolyphosphatase activity. On the other hand, induction of gemmulogenesis by theophylline results in an increase (by 61%) in polyphosphate content of sponge tissue. An increase in polyphosphate content and a d…
Purification and characterization of an exopolyphosphatase from Saccharomyces cerevisiae.
1994
An exopolyphosphatase (polyphosphate phosphohydrolase; EC 3.6.1.11) activity that cleaves inorganic polyphosphates to orthophosphate has been purified to apparent homogeneity (> 95% pure) from Saccharomyces cerevisiae. The exopolyphosphatase is a monomeric protein with a polypeptide molecular mass of 28 kDa. The enzyme, which can be stabilized in the presence of Triton X-100, has a pH optimum of 7.5 and requires, for maximal activity, Co2+ or Mg2+ ions. In the absence of these ions, the exopolyphosphatase binds to polyphosphate but does not degrade it, allowing affinity purification of the enzyme on a polyphosphate-modified zirconia support. o-Vanadate, Cu2+, and Ca2+ are effective inhibito…