海洋真菌Caldariomyces fumago产氯过氧化物酶的双水相提纯条件

采用聚乙二醇(PEG6000)在(NH4)2SO4高饱和度下沉淀夹带蛋白质富集氯过氧化物酶,再利用磷酸盐溶液复溶解共沉淀物形成的双水相萃取体系高浓度回收酶蛋白,最后再经Sephadex G100柱层析纯化获得高纯度酶试样。结果显示:氯过氧化物酶与PEG共沉淀总活力回收率达85.5%,酶在优化的PEG/磷酸盐双水相系统中上下相分配系数k在0.341以下,酶活力回收率达到69.1%,纯度提高了21.57倍,柱层析可使酶纯度进一步提高到24.79倍,总回收率为37.75%。     

The influence of body size on measurements of overall cardiac function

The purpose of this study was to determine the best scaling method to account for the effects of body size on measurements of overall cardiac function and subsequently the interpretation of data based on cardiac power output (CPO). CPO was measured at rest (CPO(rest)) and at maximal exercise (CPO(max)) on 88 and 103 healthy but untrained men and women, respectively, over the age range of 20-70 yr. Cardiac reserve (CR) was calculated as CPO(max) - CPO(rest). CPO(rest), CPO(max), and CR were all significantly related to body mass (BM), body surface area (BSA), and lean body mass (LBM). The linear regression model failed to completely normalize these measurements. In contrast, the allometric model produced size-independent values of CPO. Furthermore, all the assumptions associated with the allometric model were achieved. For CPO(rest), mean body size exponents were BM(0.33), BSA(0.60), and LBM(0.47). For CPO(max), the exponents were BM(0.41), BSA(0.81), and LBM(0.71). For CR, mean body size exponents were BM(0.44), BSA(0.87), and LBM(0.79). LBM was identified (from the root-mean-squares errors of the separate regression models) as the best physiological variable (based on its high metabolic activity) to be scaled in the allometric model. Scaling of CPO to LBM(b) (where b is the scaling exponent) dramatically reduced the between-gender differences with only a 7% difference in CPO(rest) and CPO(max) values. In addition, the gender difference in CR was completely removed. To avoid erroneous interpretations and conclusions being made when comparing data between men and women of different ages, the allometric scaling of CPO to LBM(b) would seem crucial.     

Carboxypeptidase O is a glycosylphosphatidylinositol-anchored intestinal peptidase with acidic amino acid specificity

The first metallocarboxypeptidase (CP) was identified in pancreatic extracts more than 80 years ago and named carboxypeptidase A (CPA; now known as CPA1). Since that time, seven additional mammalian members of the CPA subfamily have been described, all of which are initially produced as proenzymes, are activated by endoproteases, and remove either C-terminal hydrophobic or basic amino acids from peptides. Here we describe the enzymatic and structural properties of carboxypeptidase O (CPO), a previously uncharacterized and unique member of the CPA subfamily. Whereas all other members of the CPA subfamily contain an N-terminal prodomain necessary for folding, bioinformatics and expression of both human and zebrafish CPO orthologs revealed that CPO does not require a prodomain. CPO was purified by affinity chromatography, and the purified enzyme was able to cleave proteins and synthetic peptides with greatest activity toward acidic C-terminal amino acids unlike other CPA-like enzymes. CPO displayed a neutral pH optimum and was inhibited by common metallocarboxypeptidase inhibitors as well as citrate. CPO was modified by attachment of a glycosylphosphatidylinositol membrane anchor to the C terminus of the protein. Immunocytochemistry of Madin-Darby canine kidney cells stably expressing CPO showed localization to vesicular membranes in subconfluent cells and to the plasma membrane in differentiated cells. CPO is highly expressed in intestinal epithelial cells in both zebrafish and human. These results suggest that CPO cleaves acidic amino acids from dietary proteins and peptides, thus complementing the actions of well known digestive carboxypeptidases CPA and CPB.     

Activation of extracellular signal-regulated kinases (ERK 44/42) by chlorpyrifos oxon in Chinese hamster ovary cells

Acetylcholinesterase inhibition explains most but not all of the toxicological manifestations of exposure to the major organophosphorus insecticide chlorpyrifos (CP) and its metabolically activated form chlorpyrifos oxon (CPO); CPO is also reported to interact with muscarinic acetylcholine receptors and alter secondary messenger status. We find that CP and CPO activate extracellular signal-regulated kinases (ERK 44/42) in both wild-type (CHOK1) and human muscarinic receptor-expressing Chinese hamster ovary cells (CHO-M2). The degree of ERK 44/42 activation on treatment with 50 microM CPO for 40 minutes is 2- to 3-fold compared with control cells and is both concentration- and time-dependent. CP is at least 2-fold less potent than CPO as an activator of ERK 44/42 and the hydrolysis products 3,5,6-trichloropyridinol and diethyl phosphate are not activators. ERK 44/42 activation by CPO is insensitive to the protein kinase A inhibitor H-89, but is completely abolished by the phosphatidylinositol 3-kinase (P13-K) inhibitor wortmannin, the protein kinase C (PKC) inhibitor GF-109203X, and the mitogen-activated extracellular signal-regulated protein kinase kinase (MEK) inhibitor PD 098059. Therefore, CPO activates the ERK 44/42 signaling cascade in CHOK1 cells via a pathway dependent on P13-K, PKC, and MEK but not requiring PKA or the human M2 muscarinic receptor. In summary we find that CPO activates a mammalian signal transduction cascade involved in cell growth and differentiation. This occurs through a pathway common to growth factors and mitogens, consistent with a receptor-mediated event. However, CPO may also inhibit an enzyme involved in signal transduction. The specific target of CPO leading to the activation of ERK 44/42 and the potential effects of this activation on cell function remain to be determined.     

氯过氧化物酶发酵相关指标及其关联性分析

通过考察氯过氧化物酶(CPO)发酵相关参数的动力学特征,探究酶产量与参数之间的关联性。结果表明:CPO发酵过程中慢速C源麦芽糖比葡萄糖更有利于调控CPO的稳定合成,前者CPO最高比酶活(179.50 U/m L)比后者(135 U/m L)高出44.5 U/m L,而且产酶高峰期延迟1~2 d;发酵过程p H波动与C源消耗速率密切相关,且对CPO合成具有明显的指标性作用。通过生物量曲线及糖消耗曲线与产酶特征对比判断,菌株合成CPO为中期合成类型。副产物黑色素是菌体成熟时期的一种次生代谢物质,与酶的生物合成存在时间上的同步性。控制C源基质和p H对提高CPO稳定化生产具有一定成效。     

Continuous and Batch Production of Chloroperoxidase by Mycelial Pellets of Caldariomyces fumago in an Airlift Fermentor

Batch and continuous production of the extracellular heme glycoprotein chloroperoxidase (CPO) was studied with an airlift fermentor. We induced Caldariomyces fumago CMI 89362 to form pellets by transferring a small inoculum volume in preculture prior to growth in a 1-liter fermentor. Continuous replacement of the fructose-salts medium (dilution rate, 0.008 h⁻¹) supported continuous CPO formation at an average concentration of 128 ± 10 mg of CPO liter⁻¹ for 8 days. Optimum CPO production rates averaged 1.2 ± 0.1 mg of CPO h⁻¹ at dilution rates below 0.033 h⁻¹. Varying the carbohydrate content of the feed solution or the time of starting the feed did not significantly alter the amount of CPO produced. Batch fermentation in the airlift fermentor resulted in maximum CPO concentrations of 280 ± 80 mg of CPO liter⁻¹, although on two separate occasions CPO concentrations reached 400 to 450 mg liter⁻¹, which was double the amount obtained by free hyphae in shake flask culture.     

Stabilization of interface-binding chloroperoxidase for interfacial biotransformation

The stability of an interface-binding chloroperoxidase (CPO) against the deactivation effect of H(2)O(2) was examined. Native CPO was conjugated with polystyrene and thus self-assembled at the water-oil interface. Although the interface-assembled CPO showed improved stability as compared to native CPO, enzyme deactivation as a result of the side effect of H(2)O(2), still limits the overall productivity of the enzyme. Two approaches to further improve the stability of CPO were examined in this work. In one approach, several stabilizers including poly(ethylene glycol) (PEG), PEI, glycerol, sugars and sucrose monododecanoate were used; while in a second approach, in situ generation of hydrogen peroxide (H(2)O(2)) by using glucose oxidase (GOx) was applied. PEG was found exceptional in that it increased both the operational and storage stability of CPO. The best improvement of enzyme productivity was obtained with addition of PEG which led to an increase of 57% for interface-bound CPO and 33% for native CPO. One interesting observation with PEI is that it enhanced the storage stability against H(2)O(2) deactivation, but did not affect the enzyme's operational stability. On the other hand, glucose enhanced the operational stability by two folds, but exhibited no significant effect on storage stability. It was also found that the extended operational lifetime of CPO with in situ generation of H(2)O(2) by GOx was a result that combines the stabilizing effect of glucose and lowered concentration of H(2)O(2). Interestingly, the addition of stabilizers could improve the enantioselectivity of CPO by as much as 10%.     

Identification of a Caldariomyces fumago Mutant Secreting an Inactive Form of Chloroperoxidase Lacking the Heme Group and N-Glycans

By mutant colony screening of Caldariomyces fumago a mutant was isolated which was slightly greenish on fructose minimal medium and grew slower in comparison to the wild type. The supernatant samples lacked the Soret band typical for the heme group of the CPO and nearly no CPO activity was detected. SDS-PAGE analysis of mutant culture supernatant samples showed production of a 38–40 kDa protein while wild type samples contain the 42 kDa CPO protein. Protein identification using nanoLC-ESI-MS/MS was performed and based on three peptides the protein in the mutant culture was identified as CPO. No differences in the CPO gene sequences of wild type and mutant were found indicating a post-translational defect in protein maturation. Deglycosylation experiments using CPO from wild type and mutant were carried out. After removing N-linked oligosaccharides from wild type CPO a protein band at 38–40 kDa was detected. Our results reveal that the mutant protein lacks the heme group as well as the N-glycans.     

Deactivation mechanisms of chloroperoxidase during biotransformations

Inactivation mechanisms of chloroperoxidase (CPO) from Caldariomyces fumago have been investigated with the aim of improving the practical utility of CPO for hydrocarbon oxidation. Deactivation studies in the presence of oxidants (i.e., hydrogen peroxide and t-butyl hydroperoxide) indicated that CPO lost oxidation activity toward hydrocarbon substrates during dismutation of hydrogen peroxide. The loss of enzyme activity was accompanied by the apparent destruction of the heme rather than aggregation or denaturation of the apo-protein. The decrease of enzyme activity was significantly retarded by adding the radical scavenger t-butyl alcohol at pH 4.1, or by optimizing the reaction pH. CPO retained greatest oxidation activity at pH 5-6, which may produce a more favorable ionization state of the key amino acid (Glu-183) and thus reduce radical formation. As a result of higher activity at pH 5-6, the total turnover numbers (TTN, defined as the amount of product produced over the catalytic lifetime of the enzyme) for the oxidation of toluene and o-, m-, p-xylenes in substrate/aqueous emulsion systems ranged from ca. 10% to 110% higher at pH 5.5 (20,000 to 45,000 mol product/mol enzyme) compared to pH 4.1. Furthermore, TTNs of CPO increased with increasing turnover frequencies, indicating that higher activity toward reducing substrates reduces radical formation and stabilizes CPO toward inactivation by H(2)O(2). These findings demonstrate the important relationship between CPO stability and activity, and illustrate that large improvements in CPO activity and stability can be achieved through solvent engineering.     

Metabolism of chlorpyrifos and chlorpyrifos oxon by human hepatocytes

The metabolism of chlorpyrifos (CPS) and chlorpyrifos oxon (CPO) by human hepatocytes and human liver S9 fractions was investigated using LC-MS/MS. Cytochrome P450 (CYP)-dependent and phase II-related products were determined following incubation with CPS and CPO. CYP-related products, 3,5,6-trichloro-2-pyridinol (TCP), diethyl thiophosphate, and dealkylated CPS, were found following CPS treatment and dealkylated CPO following CPO treatment. Diethyl phosphate was not identified because of its high polarity and lack of retention with the chromatographic conditions employed. Phase II-related conjugates, including O- and S-glucuronides as well as 11 GSH-derived metabolites, were identified in CPS-treated human hepatocytes, although the O-sulfate of TCP conjugate was found only when human liver S9 fractions were used as the enzyme source. O-Glucuronide of TCP was also identified in CPO-treated hepatocytes. CPS and CPO were identified using HPLC-UV after CPS metabolism by the human liver S9 fraction. However, CPO was not found following treatment of human hepatocytes with either CPS or CPO. These results suggest that human liver plays an important role in detoxification, rather than activation, of CPS.     

Celastrus paniculatus seed oil and organic extracts attenuate hydrogen peroxide- and glutamate-induced injury in embryonic rat forebrain neuronal cells

Seed oil of Celastrus paniculatus Willd. (CP) has been reported to improve memory and the methanolic extract (ME) of CP was shown to exhibit free-radical-scavenging properties and anti-oxidant effects in human non-immortalized fibroblasts. In the present study, we have investigated the free-radical-scavenging capacity of CP seed oil (CPO) and two extracts, an ethanolic extract (EE) and a ME. CPO and EE showed dose-dependent, free-radical-scavenging capacity, but to a lesser degree than observed for ME. Oxidative stress involves the generation of free radicals and free radical scavenging is one of the mechanisms of neuroprotection. We therefore investigated the effects of CPO, ME, and EE for protection against hydrogen peroxide (H(2)O(2))- and glutamate-induced neurotoxicity in embryonic rat forebrain neuronal cells (FBNC). Pre-treatment of neuronal cells with CPO dose-dependently attenuated H(2)O(2)-induced neuronal death. Pre-treatment with ME and EE partially attenuated H(2)O(2)-induced toxicity, but these extracts were less effective than CPO for neuronal survival. In H(2)O(2)-treated cells, cellular superoxide dismutase (SOD) activity was unaffected, but catalase activity was decreased and levels of malondialdehyde (MDA) were increased. Pre-treatment with CPO, ME, or EE increased catalase activity and decreased MDA levels significantly. Also, CPO pre-treatment attenuated glutamate-induced neuronal death dose-dependently. The activity of cellular acetylcholinesterase (AChE) was not affected by CPO, ME, or EE, suggesting that the neuroprotection offered by CPO was independent of changes in AChE activity. Taken together, the data suggest that CPO, ME, and EE protected neuronal cells against H(2)O(2)-induced toxicity in part by virtue of their antioxidant properties, and their ability to induce antioxidant enzymes. However, CPO, which exhibited the least antioxidant properties, was the most effective in preventing neuronal cells against H(2)O(2)- and glutamate-induced toxicities. Thus, in addition to free-radical scavenging attributes, the mechanism of CP seed component (CP-C) neuroprotection must be elucidated.     

Association of MSX1 and TGFB3 with nonsyndromic clefting in humans.

Nonsyndromic cleft lip with or without cleft palate (CL/P) and nonsyndromic cleft palate only (CPO) are common congenital anomalies with significant medical, psychological, social, and economic ramifications. Both CL/P and CPO are examples of complex genetic traits. There exists sufficient evidence to hypothesize that disease loci for CL/P and CPO can be identified by a candidate-gene linkage-disequilibrium (LD) strategy. Candidate genes for clefting, including TGFA, BCL3, DLX2, MSX1, and TGFB3, were screened for LD with either CL/P or CPO in a predominantly Caucasian population, with both case-control- and nuclear-family-based approaches. Previously reported LD for TGFA with both CL/P and CPO could not be confirmed, except in CL/P patients with a positive family history. Also, in contrast to previous studies, no LD was found between BCL3 and either CL/P or CPO. Significant LD was found between CL/P and both MSX1 and TGFB3 and between CPO and MSX1, suggesting that these genes are involved in the pathogenesis of clefting. In addition, a mutation search in the genes DLX2, MSX1, and TGFB3 was performed in 69 CPO patients and in a subset of the CL/P patients. No common mutations were found in the coding regions of these genes; however, several rare variants of MSX1 and TGFB3 were found that may alter the latters' normal function. These results form the basis for future research, including (a) mutation searches in the MSX1 and TGFB3 genes in Caucasian CL/P patients and (b) extension of the search for MSX1 mutations in CPO patients to the noncoding regions.     

Atypical kinetic behavior of chloroperoxidase-mediated oxidative halogenation of polycyclic aromatic hydrocarbons

We have identified an atypical kinetic behavior for the oxidative halogenation of several polycyclic aromatic hydrocarbons (PAHs) by chloroperoxidase (CPO) from Caldariomyces fumago. This behavior resembles the capacity of some members of the P450 family to simultaneously recognize several substrate molecules at their active sites. Indeed, fluorometric studies showed that PAHs exist in solution as monomers and π-π dimers that interact to different extents with CPO. The dissociation constants of dimerization were evaluated for every single PAH by spectrofluorometry. Furthermore, docking studies also suggest that CPO might recognize either one or two substrate molecules in its active site. The atypical sigmoidal kinetic behavior of CPO in the oxidative halogenation of PAHs is explained in terms of different kinetic models for non-heteroatomic PAHs (naphthalene, anthracene and pyrene). The results suggest that the actual substrate for CPO in this study was the π-π dimer for all evaluated PAHs.     

Inactivation of chloroperoxidase by arginine

Inactivation of chloroperoxidase (CPO) from Caldariomyces fumago by arginine was investigated. It was found that the red native CPO solution was turned into a stable green species with a concomitant shift of the Soret band from 398 to 425 nm in the presence of arginine. The green CPO lost almost all of its catalytic activity, and this inactivation was irreversible.Differential UV–vis spectrophotometry was used to examine the binding properties of arginine to CPO. The formation of CPO-arginine (1:1) complex was highly pH-dependent. Fluorescence investigation revealed the exposure degree of prosthetic group increased. Kinetic analysis indicated that CPO has both a high affinity and specificity to arginine.This inactivation may be caused mainly by the binding of guanidinium group in arginine to the acid–base catalytic group Glu183 in CPO. The change of surrounding environment around heme induced by the interaction of heme propionates with arginine and the occupying of the sixth axial ligand position of heme iron by hydroxyl are also reasons bringing on this inactivation.     

Defining the involvement of HOCl or Cl2 as enzyme-generated intermediates in chloroperoxidase-catalyzed reactions.

Peroxidatic substrates, catechol (CAT) and 2,4,6-trimethylphenol (TMP) were used as probes of thechloride dependent reactions catalyzed by chloroperoxidase (CPO). TMP is consumed only in the presence of chloride. TMP is a competitive inhibitor versus CAT, but CAT is a noncompetitive inhibitor versus TMP in chloride-dependent CPO-catalyzed peroxidation reactions. The ratio of TMP versus CAT consumed by the chloride-dependent CPO reaction in direct competition studies increases as the chloride concentration is increased from 1.0 to 400 mM. Ratios of non-enzymatic HOCl reactions under conditions otherwise similar to those of the CPO reactions are relatively insensitive to changes in chloride concentration and are experimentally indistinguishable from the values attained by the enzyme system at high chloride concentrations. Comparison of enzymatic ratios with those of the HOCl reactions indicate that the proportion of the enzymatic reaction involving a freely dissociable, enzyme-generated, oxidized halogen species varies from 10% at low chloride concentrations to essentially 100% at high chloride concentrations. All data are consistent with a mechanism in which chloride competes with CAT for binding to both CPO compound I and the CPO chlorinating intermediate (EOCl). Chloride binding to CPO compound I leads to the formation of EOCl and initiates the CPO chloride-dependent pathway. When CAT binds to either compound I or EOCl, it is directly oxidized to product. When chloride binds to EOCl, it either induces release of HOCl or reacts with EOCl to produce Cl2, which is released from the enzyme. TMP and CAT compete for reaction with the free oxidized halogen species. This is the first direct evidence for kinetically significant involvement of a free oxidized halogen species as an intermediate in any CPO-catalyzed reaction.     

Effect of organic solvents on a chloroperoxidase biotransformation

The effect of organic solvents on the chlorination activity of chloroperoxidase (CPO) was identified for use in biotransformations with CPO. CPO was found to chlorinate monochlorodimedon (MCD) in the presence of organic solvents with log P values less than 0. The relative rates of chlorination with chloride ion in the presence of H₂O₂, buffer and 2.5–20% of either dimethyl sulfoxide, N,N-dimethyl formamide, methanol or acetonitrile, were in the range of 10–58% of that in buffer (pH 2.8) at the same reactant concentrations. The presence of such organic solvents was found to alter CPO catalysis by altering the protein conformation and the local environment at the active site. CPO did not display chlorination activity in the presence of organic solvents which had log P values greater than 0.     

One-electron reduction of chloroperoxidase by radiolytically generated electrons

Upon irradiation of aqueous ethylene glycol/water solutions of native chloroperoxidase (CPO) with 60Co-gamma rays at 77K one observes the one-electron reduction of the enzyme active site by radiolytically generated thermolyzed electrons. In the present study the first absorption spectrum of a low-spin ferrous form of CPO is reported which has peaks at 438, 532 and 563 nm, similar to those observed previously for cytochrome P-450. All previously described ferrous forms of CPO are high spin. In order to observe the final results of the CPO reaction with electrons, the spectral changes of native enzyme after room temperature-gamma-irradiation have also been investigated. Evidence of changes is also presented probably connected with disruption of the tertiary structure of enzyme, correlated with decrease of enzyme activity.     

Resonance Raman studies of isotopically labeled chloroperoxidase

Chloroperoxidase (CPO) and cytochrome P450cam have been shown by several techniques to have similar active site properties. Recent resonance Raman investigations using isotopically enriched 34S-labeled samples have demonstrated thiolate ligation in the P450cam system. We report here on a number of parallel studies involving CPO. On the basis of isotopic labeling (34S, 13CO), we assign the Fe-S and Fe-CO stretching frequencies of CPO at 347 (-vFe-S) and 488 cm-1 (-vFe-CO). The differences of the -vFe-S and -vFe-CO in CPO and P450cam may suggest subtle differences in the thiolate binding in the two systems.     

Effects of additives on the thermostability of chloroperoxidase

The effects of several polyhydroxy compounds (glucose, fructose, gumsugar, galactose, trehalose, dextran, xylose, PEG200, glycerin) and surfactant (dioctyl sulfosuccinate sodium salt, AOT) on the catalytic activity and thermal stability of chloroperoxidase (CPO) in aqueous systems were investigated at various temperatures. A 25% superactivity was found in AOT solutions at 25 degrees C, and it could be maintained during the 882 h. PEG200 and glycerin were proven to be the most efficient stabilizer for CPO in temperatures ranging from 25 to 60 degrees C. Trehalose is more helpful than other sugars for extended storage of CPO. These results are promising in view of industrial applications of this versatile biological catalyst. The protective mechanism of various additives on CPO was discussed.