Mammalian-like Purple Acid Phosphatases in Plants

Introduction Purple acid phosphatases （PAPs） comprise of a family of binuclear metal-containing hydrolases, some members of which have been isolated and characterized from animal, plant and fungal sources . PAPs not only catalyze the hydrolyses of a wide range of phosphate esters and anhydrides under acidic reaction conditions, but also catalyze the generation of hydroxyl radicals in a Fenton-like reaction, by virtue of the presence of a redox-active binuclear metal center. Inmammals,

Purple acid phosphatase promoted hydrolysis of organophosphate pesticides in microalgae

When organophosphate pesticides(OPs)are not used and handled in accordance with the current rules and standards,it results in serious threats to the aquatic environment and human health.Phaeodactylum tricornutum is a prospective microalgae-based system for pollutant removal and carbon sequestration.Genetically engineered P.tricornutum,designated as the OE line(endogenously expressing purple acid phosphatase 1[PAP1]),can utilize organic phosphorus for cellular metabolism.However,the competencies and mechanisms of the microalgae-based system(namely the OE line of P.tricornutum)for metabolizing OPs remain to be addressed.In this study,the OE line exhibited the effective biodegradation competencies of 72.12%and 68.2%for 30 mg L^(-1)of dichlorvos and 50 mg L^(-1)of glyphosate,accompanied by synergistic accumulations of biomass(0.91 and 0.95 g L^(-1))and lipids(32.71%and 32.08%),respectively.Furthermore,the biodiesel properties of the lipids from the OE line manifested a high potential as an alternative feedstock for microalgae-based biofuel production.A plausible mechanism of OPs biodegraded by overexpressed PAP1 is that sufficient inorganic P for adenosine triphosphate and concurrent carbon flux for the reduced form of nicotinamide adenine dinucleotide phosphate biosynthesis,which improved the OP tolerance and biodegradation competencies by regulating the antioxidant system,delaying programmed cell death and accumulating lipids via the upregulation of related genes.To sum up,this study demonstrates a potential strategy using a genetically engineered strain of P.tricornutum to remove high concentrations of OPs with the simultaneous production of biomass and biofuels,which might provide novel insights for microalgae-based pollutant biodegradation.

Inhibition of Model Compound of Purple Acid Phosphatases on Growth of Aerobacter aerogenes Investigated by Microcalorimetry

Microcalorimetry was used to study the inhibitory or antibiotic action of six kinds of the model compounds of purple acid phosphatases on a strain of Aerobacter aerogenes . Difference in their capacities to inhibit the metabolism of this bacterium was observed. The extent and duration of the inhibitory effect on the metabolism as judged from the growth rate constant, k , and the half inhibitory concentration, IC 50 , varied with the different drugs. The rate constant k of A. aerogenes (in the log phase) in the presence of the compounds decreased with the increasing of concentrations. The experimental results reveal that the order of the antibiotic activity of the compounds is: LD 1>LD 2>LD 3>XF 1>LD 4～LD 5.

Phytate:impact on environment and human nutrition.A challenge for molecular breeding

Phytic acid (PA) is the primary storage compound of phosphorus in seeds accounting for up to 80% of the total seed phosphorus and contributing as much as 1.5% to the seed dry weight. The negatively charged phosphate in PA strongly binds to metallic cations of Ca, Fe, K, Mg, Mn and Zn making them insoluble and thus unavailable as nutritional factors. Phytate mainly accumulates in protein storage vacuoles as globoids, predominantly located in the aleurone layer (wheat, barley and rice) or in the embryo (maize). During germination, phytate is hydrolysed by endogenous phytase(s) and other phosphatases to release phosphate, inositol and micronutrients to support the emerging seedling. PA and its derivatives are also implicated in RNA export, DNA repair, signalling, endocytosis and cell vesicular trafficking. Our recent studies on purification of phytate globoids, their mineral composition and dephytinization by wheat phytase will be discussed. Biochemical data for purified and characterized phytases isolated from more than 23 plant species are presented, the dephosphorylation pathways of phytic acid by different classes of phytases are compared, and the application of phytase in food and feed is discussed.

Overexpression of OsPAP10a, A Root-Associated Acid Phosphatase, Increased Extracellular Organic Phosphorus Utilization in Rice

Phosphorus （P） deficiency is a major limitation for plant growth and development. Among the wide set of responses to cope with low soil P, plants increase their level of intracellular and secreted acid phosphatases （APases）, which helps to catalyze inorganic phosphate （Pi） hydrolysis from organophosphates, in this study we characterized the rice （Oryza sativa） purple acid phosphatase 10a （OsPAPIOa）. OsPAPIOa belongs to group la of purple acid phosphatases （PAPs）, and clusters with the principal secreted PAPs in a variety of plant species including Arabidopsis. The transcript abundance of OsPAPIOa is specifically induced by Pi deficiency and is controlled by OsPHR2, the central transcription factor controlling Pi homeostasis. In gel activity assays of root and shoot protein extracts, it was revealed that OsPAPIOa is a major acid phosphatase isoform induced by Pi starvation. Constitutive overexpression of OsPAPIOa results in a significant increase of phosphatase activity in both shoot and root protein extracts. In vivo root 5-bromo.4-chloro-3-indolyl-phosphate （BCIP） assays and activity measurements on external media showed that OsPAPIOa is a root-associated APase. Furthermore, overexpression of OsPAPIOa significantly improved ATP hydrolysis and utilization compared with wild type plants. These results indicate that OsPAPIOa can potentially be used for crop breeding to improve the efficiency of P use.