Alkaline phosphatase

About: Alkaline phosphatase is a research topic. Over the lifetime, 20218 publications have been published within this topic receiving 540547 citations. The topic is also known as: Alkaline_phosphatase & IPR001952.

Distribution of microbial- and root-derived phosphatase activities in the rhizosphere depending on P availability and C allocation – Coupling soil zymography with 14C imaging

Abstract: Despite its importance for terrestrial nutrient and carbon cycling, the spatial organization of microbial activity in soil and in the rhizosphere is poorly understood. We related carbon allocation by roots to distribution of acid and alkaline phosphatase activity in the rhizosphere of Lupinus albus L. To do so, we further developed soil zymography – an in situ method for the analysis of the two-dimensional distribution of enzyme activity in soil – integrating fluorescent substrates. Soil zymography was combined with 14C imaging, a technique that gives insights into the distribution of photosynthates after labeling plants with 14C. Both acid and alkaline phosphatase activity were up to 5.4-times larger in the rhizosphere than in the bulk soil. While acid phosphatase activity (produced by roots and microorganisms) was closely associated with roots, alkaline phosphatase activity (produced only by microorganisms) was more widely distributed, leading to a 2.5-times larger area of activity of alkaline than of acid phosphatase. These results indicate a spatial differentiation of different ecophysiological groups of organic P mineralizing organisms. The spatial differentiation could be either between microorganisms and L. albus or between microorganisms that produce exclusively alkaline phosphatases on the one hand, and L. albus and root associated microorganisms that produce acid phosphatases on the other hand. The spatial separation of different organic P mineralizing organisms might alleviate a potential competition between them. While alkaline phosphatase activity strongly decreased with P fertilization, acid phosphatase activity was not affected by fertilization, suggesting that alkaline phosphatase-producing microorganisms react more strongly to it than other organic P mineralizing organisms. Alkaline phosphatase activity was high in parts of the rhizosphere where relatively little recent photosynthates were allocated, indicating that rhizodeposition and the activity of alkaline phosphatase-producing microorganisms are not directly related. Our study indicates, first, a spatial differentiation of organic P mineralization by various ecophysiological groups that react differently to inorganic P fertilization and second, that rhizodeposition and alkaline phosphatase-producing microorganisms were not directly related. Finally, we conclude that soil zymography with fluorescent substrates is a very promising approach for studying the distribution of a broad range of extracellular enzymes at microscales.

Effects of hydrogen peroxide (H2O2) on alkaline phosphatase activity and matrix mineralization of odontoblast and osteoblast cell lines

Abstract: Hydrogen peroxide (H2O2), an oxidizing agent, has been widely used as a disinfectant. Recently, because of its reactive properties, H2O2 has also been used as a tooth bleaching agent in dental care. This is a cause for concern because of adverse biological effects on the soft and hard tissues of the oral environment. To investigate the influence of H2O2 on odontoblasts, the cells producing dentin in the pulp, we assessed cellular viability, generation of reactive oxygen species (ROS), alkaline phosphatase (ALP) activity, and nodule formation of an odontoblastic cell line (MDPC-23) after treatment with H2O2, and compared those with the effects on preosteoblastic MC3T3-E1 cells. Cytotoxic effects of H2O2 began to appear at 0.3 mmol/L in both MDPC-23 and MC3T3-E1 cells. At that concentration, the accumulation of intracellular ROS was confirmed by a fluorescent probe, DCFH-DA. Although more ROS were detected in MDPC-23, the increasing pattern and rate are similar between the two cells. When the cells were treated with H2O2 at concentrations below 0.3 mmol/L, MDPC-23 displayed a significant increase in ALP activity and mineralized bone matrix, while MC3T3-E1 cells showed adverse effects of H2O2. It is known that ROS are generally harmful by-products of aerobic life and represent the primary cause of aging and numerous diseases. These data, however, suggest that ROS can induce in vitro cell differentiation, and that they play a more complex role in cell physiology than simply causing oxidative damage.

Alkaline phosphatase: beyond the liver.

Abstract: The alkaline phosphatases comprise a heterogeneous group of enzymes that are widely distributed in mammalian cells. They often are associated with cell membranes, but their exact physiologic function is unknown. Despite this, alkaline phosphatase activity is a very useful serum biochemical indicator of liver disease, particularly cholestatic disease. However, increases in the activity of alkaline phosphatase in serum and other body fluids may reflect physiologic or pathologic changes beyond those of hepatic origin. For example, nonhepatic increases in serum alkaline phosphatase activity are found in young animals, in pregnant and lactating females, and in association with high fat diets. Bone disease, endocrine disease, neoplasia, and other disorders can result in increased alkaline phosphatase activity. In addition, alkaline phosphatase activity may be increased due to induction by certain drugs such as glucocorticoids and anticonvulsants. In this article, we will review the physiologic and pathologic factors influencing the activity of alkaline phosphatase in serum and other body fluids, with an emphasis on disorders beyond liver disease.

Novel Inhibitors of Alkaline Phosphatase Suppress Vascular Smooth Muscle Cell Calcification

Abstract: We report three novel inhibitors of the physiological pyrophosphatase activity of alkaline phosphatase and show that these compounds are capable of reducing calcification in two models of vascular calcification (ie, they suppress in vitro calcification by cultured Enpp1−/− VSMCs and they inhibit the increased pyrophosphatase activity in a rat aortic model) Introduction: Genetic ablation of tissue-nonspecific alkaline phosphatase (TNALP) leads to accumulation of the calcification inhibitor inorganic pyrophosphate (PPi) TNALP deficiency ameliorates the hypermineralization phenotype in Enpp1−/− and ank/ank mice, two models of osteoarthritis and soft tissue calcification We surmised that the pharmacological inhibition of TNALP pyrophosphatase activity could be used to prevent/suppress vascular calcification Materials and Methods: Comprehensive chemical libraries were screened to identify novel drug-like compounds that could inhibit TNALP pyrophosphatase function at physiological pH We used these novel compounds to block calcification by cultured vascular smooth muscle cells (VSMCs) and to inhibit the upregulated pyrophosphatase activity in a rat aortic calcification model Results: Using VSMC cultures, we determined that Enpp1−/− and ank/ank VSMCs express higher TNALP levels and enhanced in vitro calcification compared with wildtype cells By high-throughput screening, three novel compounds, 5361418, 5923412, and 5804079, were identified that inhibit TNALP pyrophosphatase function through an uncompetitive mechanism, with high affinity and specificity when measured at both pH 98 and 75 These compounds were shown to reduce the calcification by Enpp1−/− VSMCs Furthermore, using an ex vivo rat whole aorta PPi hydrolysis assay, we showed that pyrophosphatase activity was inhibited by all three lead compounds, with compound 5804079 being the most potent at pH 75 Conclusions: We conclude that TNALP is a druggable target for the treatment and/or prevention of ectopic calcification The lead compounds identified in this study will serve as scaffolds for medicinal chemistry efforts to develop drugs for the treatment of soft tissue calcification