The role of acid phosphatases in plant phosphorus metabolism

Hydrolysis of phosphate esters is a critical process in the energy metabolism and metabolic regulation of plant cells. This review summarizes the characteristics and putative roles of plant acid phosphatase (APase). Although immunologically closely related, plant APases display remarkable heterogeneity with regards to their kinetic and molecular properties, and subcellular location. The secreted APases of roots and cell cultures are relatively non-specific enzymes that appear to be important in the hydrolysis and mobilization of P_i from extracellular phosphomonoesters for plant nutrition. Intracellular APases are undoubtedly involved in the routine utilization of P_i reserves or other P_i-containing compounds. A special class of intracellular APase exists that demonstrate a clear-cut (but generally nonabsolute) substrate selectivity. These APases are hypothesized to have distinct metabolic functions and include: phytase, phosphoglycolate phosphatase, 3-phosphoglycerate phosphatase, phosphoenolpyruvate phosphatase, and phosphotyrosyl-protein phosphatase. APase expression is regulated by a variety of developmental and environmental factors. P_i starvation induces de novo synthesis of extra- and intracellular APases in cell cultures as well as in whole plants. Recommendations are made to achieve uniformity in the analyses of the different APase isoforms normally encountered within and between different plant tissues.     

The role of acid phosphatase activity during enzymic dephosphorylation of phytates byAspergillus niger phytase

Acid phosphatase present in preparations ofAspergillus niger phytase accelerated dephosphorylation of sodium phytate. Its influence on the reaction rate and distribution ofmyo-inositol phosphates was most apparent at low pH value (2.5) and when acid-hydrolysed substrate was de-esterified enzymatically. With partly purified phytase, the predominant inositol form was tetraphosphate but a preparation having acid phosphatase activity caused an even distribution of lower inositol phosphates after a few hours.     

Biochemical changes during germination and seedling growth in Cuscuta campestris

Changes in the contents of starch, protein, DNA, RNA, total phosphorus, acid soluble phosphorus and inorganic phosphorus, and in the activities of some enzymes of carbohydrate, amino acid, nucleic acid and phosphate metabolism were studied during the germination of Cuscuta campestris seeds. The results are expressed on per seed basis.
Starch content in Cuscuta seeds showed a steady decline with most of it depleted by the end of the eighth day of germination. Protein content increased with germination up to 48 h and then decreased. RNA and DNA contents increased to a maximal level on the fourth day of germination and then decreased. Total phosphorus in the seeds remained almost unchanged during the period of study. Both trichloroacetic acid soluble and inorganic phosphorus increased until the third day and then decreased. Phytin was rapidly hydrolyzed with little being detectable by the seventh day of germination. Glucose-6-phosphate dehydrogenase increased with germination, while fructose bisphosphate aldolase which is indispensable for glycolysis, decreased with germination. Ribonuclease and deoxyribonuclease increased till the third and fourth day, respectively, and then decreased. Aspartate and alanine aminotransferases showed a maximum on the second day and then decreased. Activities of alkaline fructose-1,6-bisphosphatase and phytase were absent in the dry seeds and appeared only on the second day of germination. Both α- and β-amylase activities were present in the dry seed.     

Mineralization of dissolved organic phosphorus from a shallow eutrophic lake

Release of soluble reactive phosphorus (SRP) from dissolved organic phosphorus (DOP), concentrated by reverse osmosis of water samples from Lough Neagh Northern Ireland, was measured in the presence of enzymes and cultures of lake water bacteria in a basal liquid medium adjusted to the pH of lake water (7.6). No hydrolysis of unfractionated DOP was observed in the presence of alkaline phosphatase but a combination of alkaline phosphatase and phosphodiesterase mineralized 14% of DOP in a 30 day incubation period at 15 °C. A similar amount of mineralization was attained by phytase. Phytase induced the same degree of mineralization in a range of DOP fractions varying from MW > 100 000 to c. 500. A mixed culture of lake water bacteria mineralized 12% of unfractionated DOP. Single cultures of lake water bacteria displayed low mineralizing activity (mean of 49 cultures = 5% DOP hydrolysed). Results indicate that DOP from Lough Neagh in the above molecular weight range is predominantly recalcitrant to bacterial mineralization under natural lake conditions.     

植酶Q9对大田遮阴夏玉米产量和衰老特性的调控作用

黄淮海夏季太阳辐射量降低以及种植密度增加引起了夏玉米冠层光照不足,产量大幅降低。本试验选用夏玉米品种‘登海605'(DH605)为试验材料,设置3个遮阴处理:花粒期遮阴(S₁)、穗期遮阴(S₂)和全生育期遮阴(S₃),以大田自然光照为对照(CK),并选用化控试剂植酶Q9(原液稀释100倍)对遮阴处理和CK进行外源调控,即花粒期遮阴-植酶Q9(S₁Q)、穗期遮阴-植酶Q9(S₂Q)、全生育期遮阴-植酶Q9(S₃Q)及大田自然光照-植酶Q9(CKQ),化控处理以同时期喷施清水为对照,探讨植酶Q9对大田遮阴夏玉米衰老特性的调控作用。结果表明: 遮阴显著降低了夏玉米的叶面积指数(LAI)、功能叶片叶绿素相对含量值(SPAD值)和净光合速率,进而显著降低了夏玉米产量。同时,遮阴夏玉米穗位叶的超氧物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性显著降低,丙二醛(MDA)、游离脯氨酸含量显著增加,可溶性蛋白含量显著降低。喷施植酶Q9后,S₃Q和S₂Q的LAI、功能叶片SPAD值和净光合速率显著提高;S₃Q、S₂Q、S₁Q的MDA和游离脯氨酸含量显著降低,可溶性蛋白含量和POD活性显著提高,S₂Q、S₃Q各时期的SOD和CAT活性显著提高;S₃Q、S₂Q、S₁Q的产量分别较S₃、S₂、S₁平均提高19%、8%、7%,CKQ与CK间无显著差异。因此,喷施植酶Q9通过提高弱光胁迫下夏玉米的光合能力,延缓叶片的衰老,增加产量,可有效缓解弱光胁迫导致的减产危害。     

Dietary metabolizable energy,digestible lysine,available phosphorus levels and exogenous enzymes affect broiler chicken performance

The nutritional composition of diets and the provision of exogenous enzymes play important roles in animal performance. Here, we evaluated the individual and combined impact of nutrients (metabolizable energy (ME), digestible lysine (dLys), available phosphorus and calcium (avP–Ca)) and exogenous multicarbohydrase and phytase complex (MCPC) enyzmes on the growth performance and feed efficiency of broiler chickens from 10 to 42 days (d) of age. Experimental diets were formulated in a Box-Behnken design to contain various levels of ME (11.89, 12.21, 12.54 or 13.06 MJ/kg), dLys (0.91%, 0.93%, 0.96% or 1.00%) and avP/Ca (0.12/0.47%, 0.21/0.58% or 0.33/0.68%). The effect of MCPC was expressed in terms of the extra nutrients released. The diets were formulated to have consistent substrate contents (i.e., arabinoxylan and phytate). Feed intake (FI), BW gain (BWG) and feed conversion ratio (FCR) were described via polynomial equations (R² = 0.99, 0.98 and 0.81, respectively), with interconnections between variables (ME, dLys and avP–Ca). Available P–Ca was the most important factor affecting FI (quadratically), and BWG and FCR (linearly). Reducing the avP content from 0.33% to 0.12% in diets lacking MCPC resulted in 25% and 33% decreases in FI and BWG, respectively, and a 12% increase in FCR. The ME and dLys contents also linearly affected these performance parameters to a lesser degree; FI decreased by 400 g when the ME was reduced by 1.17 MJ/kg, and by 300 g following a 0.09% reduction of dLys, while the same reductions in ME and dLys decreased BWG by 120 g and 150 g, respectively. The inclusion of MCPC alleviated the reduction of FI, BWG and FCR by decreasing the avP–Ca. Thus, ME and dLys were the most important factors affecting BWG and FCR in broilers fed diets containing MCPC. When MCPC was added, ME negatively affected FI (r = −0.89, P < 0.001), whereas the dLys content was correlated with BWG (r = 0.74, P < 0.001). Both ME and dLys affected FCR (r = −0.83 and −0.85, respectively). Supplementing MCPC allowed the reduction of ME, dLys and avP–Ca in the diet without affecting performance. Indeed, MCPC’s effect promoted with the release of the following nutrients: 0.56 MJ ME/kg, 0.06% dLys, and 0.15% and 0.13% avP and Ca, respectively. The results indicate nutrient effect and interaction on performance and feed additive potential for nutrient release.     

Purification and kinetics of a protease-resistant,neutral, and thermostable phytase from Bacillus subtilis subsp. subtilis JJBS250 ameliorating food nutrition

Abstract

A novel protease-resistant and thermostable phytase from Bacillus subtilis subsp. subtilis JJBS250 was purified 36-fold to homogeneity with a combination of ammonium sulfate precipitation followed by Q-Sepharose and Sephadex G-50 chromatographic techniques. The estimated molecular mass of the purified phytase was 46?kDa by electrophoresis with optimal activity at pH 7.0 and 70?°C. About 19% of original activity was maintained at 80?°C for 10?min. Phytase activity was stimulated in presence of surfactants like Tween-20, Tween-80, and Triton X-100 and metal ions like Ca⁺², K⁺, and Co⁺² and it was inhibited by SDS and Mg⁺², Al⁺², and Fe⁺². Purified enzyme showed specificity to different salts of phytic acid and values of K_m and V_max were 0.293?mM and 11.49 nmoles s^?1, respectively for sodium phytate. The purified enzyme was resistant to proteases (trypsin and pepsin) that resulted in amelioration of food nutrition with simultaneous release of inorganic phosphate, reducing sugars, and soluble protein.     

Standardized total tract digestible phosphorus requirement of 6 to 13 kg pigs fed diets without or with phytase

Dietary phosphorus concentration greatly affects pig’s growth performance, environmental impact and diet cost. A total of 1080 pigs (initially 5.9 ± 1.08 kg) from three commercial research rooms were used to determine the effects of increasing standardized total tract digestible (STTD) P concentrations in diets without and with phytase on growth performance and percentage bone ash. Pens (10 pigs/pen, 9 pens/treatment) were balanced for equal weights and randomly allotted to 12 treatments. Treatments were arranged in two dose titrations (without or with 2000 units of phytase) with six levels of STTD P each. The STTD P levels were expressed as a percentage of NRC (2012) requirement estimates (% of NRC; 0.45 and 0.40% for phases 1 and 2, respectively) and were: 80%, 90%, 100%, 110%, 125% and 140% of NRC in diets without phytase and 100%, 110%, 125%, 140%, 155% and 170% of NRC in diets with phytase. Diets were provided in three phases, with experimental diets fed during phases 1 (days 0 to 11) and 2 (days 11 to 25), followed by a common diet from days 25 to 46. On day 25, radius samples from one median-weight gilt per pen were collected for analysis of bone ash. During the treatment period, increasing STTD P from 80% to 140% of NRC in diets without phytase improved average daily gain (ADG; quadratic, P < 0.01), average daily feed intake (ADFI; quadratic, P < 0.05) and gain–feed ratio (G : F; linear, P < 0.01). Estimated STTD P requirement in diets without phytase was 117% and 91% of NRC for maximum ADG according to quadratic polynomial (QP) and broken-line linear (BLL) models, respectively, and was 102%, 119% and >140% of NRC for maximum G : F using BLL, broken-line quadratic and linear models, respectively. When diets contained phytase, increasing STTD P from 100% to 170% of NRC improved ADG (quadratic, P < 0.05) and G : F (linear, P < 0.01). Estimated STTD P requirement in diets containing phytase was 138% for maximum ADG (QP), and 147% (QP) and 116% (BLL) of NRC for maximum G : F. Increasing STTD P increased (linear, P < 0.01) the percentage bone ash regardless of phytase addition. When comparing diets containing the same STTD P levels, phytase increased (P < 0.01) ADG, ADFI and G : F. In summary, estimated STTD P requirements varied depending on the response criteria and statistical models and ranged from 91% to >140% of NRC (0.41% to >0.63% of phase 1 diet and 0.36% to >0.56% of phase 2 diet) in diets without phytase, and from 116% to >170% of NRC (0.52% to >0.77% of phase 1 diet and 0.46% to >0.68% of phase 2 diet) for diets containing phytase. Phytase exerted an extra-phosphoric effect on promoting pig’s growth and improved the P dose-responses for ADG and G : F.     

Sparing effect of microbial phytase on zinc supplementation in maize-soya-bean meal diets for chickens

The experiment was conducted to evaluate the sparing effect of microbial phytase on the need for dietary zinc supplementation in chicks. A maize–soya-bean meal basal diet, containing 33 mg of zinc and 16 mg of copper per kg, supplemented with 0, 6, 12, 18, 24, 30 or 60 mg of zinc as sulphate per kg or with 250, 500, 750 or 1000 units (FTU) of microbial phytase (3-phytase from Aspergillus niger, Natuphos®) per kg was given to 1-day-old chicks for 20 days. Sixteen chicks placed in individual cages were assigned to each diet except the unsupplemented basal diet which was assigned to 32 cages. Actual range of phytase supplementation was 280 to 850 FTU per kg diet. Growth performance was not affected by microbial phytase. Chicks given the unsupplemented basal diet and the basal diet supplemented with 60 mg of zinc per kg displayed similar performance. Bone weight, bone ash, liver weight and liver dry matter were independent (P > 0.1) of zinc and phytase supplementations. Plasma, bone and liver zinc concentrations increased linearly (P < 0.001) and quadratically (P < 0.001; P < 0.001 and P < 0.05, respectively) with zinc added. Plasma zinc tended to increase linearly (P = 0.07) and bone zinc increased linearly (P < 0.01) with phytase added but no quadratic response was detected (P > 0.1). Liver zinc was unresponsive to phytase added (P > 0.1). Liver copper decreased linearly (P < 0.001) and quadratically (P < 0.01) with zinc supplementation. Mathematical functions were fitted to the responses of plasma and bone zinc to zinc and phytase added and used to calculate zinc equivalency values of phytase. The models included a linear plateau response to zinc added and a linear response to phytase added. In diets without phytase, plasma and bone zinc concentrations were maximised for a dietary zinc concentration of 55 and 51 mg/kg, respectively. Over the range of 280 to 850 FTU, 100 FTU was equivalent to 1 mg of zinc as sulphate. Consequently, in a maize–soya-bean meal chicken diet formulated to contain 60 mg zinc per kg, zinc ingested, and in turn, zinc excreted may be reduced by around 10% if the diet contains 500 FTU as Natuphos® per kg.     

Phytase activity in Cryptococcus laurentii ABO 510

Ten Cryptococcus strains were screened for phytase activity, of which the Cryptococcus laurentii ABO 510 strain showed the highest level of activity. The cell wall-associated enzyme displayed temperature and pH optima of 62 degrees C and 5.0, respectively. The enzyme was thermostable at 70 degrees C, with a loss of 40% of its original activity after 3 h. The enzyme was active on a broad range of substrates, including ATP, D-glucose 6-phosphate, D-fructose 1,6-diphosphate and p-nitrophenyl phosphate (p-NPP), but its preferred substrate was phytic acid (K(m) of 21 microM). The enzyme activity was completely inhibited by 0.5 mM inorganic phosphate or 5 mM phytic acid, and moderately inhibited in the presence of Hg(2+), Zn(2+), Cd(2+) and Ca(2+). These characteristics suggest that the Cry. laurentii ABO 510 phytase may be considered for application as an animal feed additive to assist in the hydrolysis of phytate complexes to improve the bioavailability of phosphorus in plant feedstuff.