头孢菌素酰化酶

7-氨基头孢烷酸(7-amino cephalosporanic acid, 7-ACA)是医药工业合成大多数头孢菌素的重要原料.头孢菌素酰化酶(cephalosporin acylase, CA)催化头孢菌素C(CPC)和戊二酰-7-氨基头孢烷酸(GL-7ACA)的水解反应, 生成7-ACA.根据CA催化底物的不同, 可将其划分为两类：CPC酰化酶和GL-7ACA酰化酶.由CA的同源性、分子质量大小和基因结构, 可以把头孢菌素酰化酶划分为五种;讨论了酶的基本性质.通过CA与N端亲核水解酶(Ntn水解酶)的比较, 推测CA属于Ntn水解酶, 并由此可以进一步理解它们的生理功能.     

5岁以下哮喘患儿血清过敏原病例对照研究及相关性分析

摘要 目的：探讨5岁以下哮喘儿童与血清特异性过敏原（specific IgE,sIgE）的分布情况。方法：本研究采用免疫印迹法对 2019 年1月至 2019 年12月在西安交通大学第二附属医院住院的5岁以下62例哮喘患儿和49例喘息患儿的行血清特异性过敏原检测,对比分析5岁以下哮喘和喘息儿童过敏原分布情况及与哮喘的发病关系。结果：户尘螨、猫毛皮屑、狗毛皮屑、蒿草、葎草、桤杨柳山毛榉橡胡桃、烟曲霉、念珠菌点青霉分枝孢霉交链孢霉黑曲霉吸入过敏原和花生黄豆、腰果开心果榛子杏仁核桃、虾蟹、桃苹果芒果荔枝草莓食物过敏原这12类过敏原在哮喘组与喘息组有显著差异（P<0.05）,与哮喘发病有关。多因素logistic回归分析结果显示户尘螨、猫毛皮屑、坚果类、霉菌、水果类是哮喘发病的危险因素（P<0.05）。户尘螨、猫毛皮屑和虾蟹是男性哮喘患儿发病的危险因素,念珠菌点青霉分枝孢霉交链孢霉黑曲霉是女性哮喘患儿发病的危险因素（P<0.05）。结论：血清特异性（sIgE）过敏原在哮喘与喘息患儿中分布不同,同时发现过敏原在哮喘患儿中存在性别差异,故对哮喘患儿进行过敏性检测可以作为回避过敏原的依据。     

Production of cephalosporin C,and its intermediates,by raised-titre strains of Acremonium chrysogenum

Three different strains of Acremonium chrysogenum have been grown under identical fermentation conditions and their profiles with respect to cephalosporin C and its intermediates were compared. Clear differences were found between the strains; one notably accumulated a large pool of penicillin N, showing a reduced ability to convert this antibiotic to the later intermediates in the pathway, deacetoxycephalosporin C, deacetylcephalosporin C and cephalosporin C.     

A comparative biochemical study of conifer pollen allergens

In the order Coniferales, only the family Cupressaceae is regarded as being a significant source of airborne allergens, withJuniperus ashei characterized as the most significat aeroallergen. Pollen of the closely related speciesJ. virginiana has been shown to cross-react withJ. ashei pollen, however,J. virginiana pollen is not considered an important aeroallergen. Although there have been several reports of allergies toPinus pollen, the pollen of this genus is regarded as hypoallergenic. Our previous studies have shown that pollen extracts ofJ. ashei, J. virginiana, J. pinchotii, Cupressus macrocarpa, Pinus echinata andP. taeda all contained several proteins with the same molecular weights including the reported allergen ofJ. ashei. The present study compared the biochemistry ofJ. ashei, J. virginiana andP. echinata pollen. A time course experiment ofJ. ashei, J. virginiana andP. echinata showed thatJ. ashei released a greater quantity of protein within the first minute of moistening. SDS-PAGE analyses showed that the reported allergen ofJ. ashei pollen extracts was released in large quantities within the first minute of extraction. It was also determined that individual pollen grains ofP. echinata contained a greater quantity of protein than the pollen ofJ. ashei andJ. virginiana, but due to the large size of pine pollen there was less protein per gram of pollen. Lipid analysis of these three taxa showed that the pollen ofP. echinata contained more lipid per grain and per gram of pollen. Results indicate that the rapid release of the reported allergen fromJ. ashei pollen contributes to the allergenicity of this species compared to bothJ. virginiana andP. echinata.     

Fusion protein of Vitreoscilla hemoglobin with D-amino acid oxidase enhances activity and stability of biocatalyst in the bioconversion process of cephalosporin C

In this study we constructed an artificial flavohemoprotein by fusing Vitreoscilla hemoglobin (VHb) with D-amino acid oxidase (DAO) of Rhodotorula gracilis to determine whether bacterial hemoglobin can be used as an oxygen donor to immobilized flavoenzyme. This chimeric enzyme significantly enhanced DAO activity and stability in the bioconversion process of cephalosporin C. In a 200-mL bioreactor, the catalytic efficiency of immobilized VHb-DAO against cephalosporin C was 12.5-fold higher than that of immobilized DAO, and the operational stability of the immobilized VHb-DAO was approximately threefold better than that of the immobilized DAO. In the scaled-up bioprocess with a 5-L bioreactor, immobilized VHb-DAO (2500 U/L) resulted in 99% bioconversion of 120 mM cephalosporin C within 60 min at an oxygen flow rate of 0.2 (v/v) x min. Ninety percent of the initial activity of immobilized VHb-DAO could be maintained at up to 50 cycles of the enzymatic reaction without exogenous addition of H(2)O(2) and flavin adenine dinucleotide (FAD). The purity of the final product, glutaryl-7-aminocephalosporanic acid, was confirmed to be 99.77% by high-performance liquid chromatography (HPLC) analysis. Relative specificity of immobilized VHb-DAO on D-alpha-aminoadipic acid, a precursor in cephalosporin C biosynthesis, increased twofold, compared with that of immobilized DAO, suggesting that conformational modification of the VHb-DAO fusion protein may be altered in favor of cephalosporin C.     

Intrauterine sensitization of ovalbumin in the third trimester increases the risk of food allergy in progeny

Intrauterine sensitization caused by food allergens plays an important role in the food allergy development in progeny. The aim of our study was to determine the critical period of intrauterine sensitization during pregnancy. Female mice were exposed to ovalbumin (OVA) during different trimesters of pregnancy. Lymphocytes from their offspring were isolated and cultured, and proliferation was evaluated by CCK-8 assay. The levels of IFN-γ and IL-4 in serum were measured using ELISA. In addition, the expressions of IFN-γ and IL-4 mRNAs and proteins were detected by real-time PCR and western blot. The mice were divided into the first trimester pregnancy (FTP1 and FTP2) group, the second trimester pregnancy (STP1 and STP2) group, and the third trimester pregnancy (TTP1 and TTP2) group based on the stages of pregnancy in which their mothers were exposed to OVA and their ages. The OVA-specific lymphocyte proliferation of the TTP1 group was statistically significantly greater that in the FTP1 and STP1 groups. The serum level of IFN-γ in the TTP1 group was significantly decreased, and the serum level of IL-4 in the TTP1 group was significantly increased compared with the levels in the FTP1 and STP1 groups. The mRNA and protein expression levels of IFN-γ in the TTP1 group were significantly decreased and the mRNA and protein expression levels of IL-4 in this group were significantly increased compared with the levels in the FTP1 and STP1 groups. Our results suggest that OVA-induced intrauterine sensitization in the third trimester may increase the risk of food allergy after birth.     

Isolation and characterization of pollen-specific maize genes with sequence homology to ragweed allergens and pectate lyases

A cDNA clone (Zm58.1) was isolated by differential screening from a cDNA library made to mature Zea mays pollen, and shown to be pollen-specific by RNA blot analysis. When this partial-length clone was used to probe a genomic library, a similar but distinct pollen-specific genomic clone (68% sequence identity) was isolated (Zm58.2). The putative proteins coded for by these two clones show sequence homology to several flower-expressed gene products from various plant species, including known pollen allergens from short ragweed (Ambrosia artemisiifolia), and to pectate lyases from the plant pathogenic bacteria Erwinia spp. The two genes map to different chromosomes.     

The polyprotein allergens of nematodes (NPAs) - structure at last, but still mysterious

We are engaged in structural and functional studies of several types of lipid binding protein that are only found in nematodes. Amongst these are the nematode polyprotein allergens (NPAs) and we now report the solution structure of ABA-1A (As-NPA-A1), the most repeated unit within the NPA array of Ascaris suum, which is almost identical in amino acid sequence to that of Ascaris lumbricoides. The protein forms a slightly flattened, compact, globular fold consisting of a long central helix that participates in two flanking helical bundles. Two pockets lined with apolar amino acid sidechains are apparent, one in the carboxy-terminal region of the protein, and another smaller one in the amino-terminal region. The former appears to be the main site of fatty acid binding, and the latter may have different, though possibly overlapping, ligand binding propensities. The structure of the binding sites indicates that lipid ligands are anchored within them with their hydrophobic tails oriented towards the core of the protein and their polar headgroups bound to charged sidechains at the mouth of the pockets. The three-dimensional architectures of the amino- and carboxy-terminal halves of ABA-1A are closely similar, thereby strengthening the long-suspected idea that the repeated units of NPAs themselves originate from an ancient duplication event.     

Intraparticle concentration gradients for substrate and acidic product in immobilized cephalosporin C amidase and their dependencies on carrier characteristics and reaction parameters

Cephalosporin C amidase was covalently attached using a protein loading of 7.0–200 mg protein/g dry carrier on four epoxy‐activated Sepabeads differing in particle size and pore diameter. Initial‐rate kinetic analysis showed that for Sepabeads with small pore diameters (30–40 nm), the apparent K_M of the amidase for hydrolysis of cephalosporin C at 37°C and pH 8.0 increased ～3‐fold in response to increased particle size (～120–400 µm) and increased amount of immobilized enzyme (7.0–70 mg protein/g dry carrier) while maximum specific activity (3.2 U/mg protein; 25% of free amidase) was affected only by particle size. In contrast, for Sepabeads with wide pores (150–250 nm), the K_M was independent of the enzyme loading. Internal effectiveness factors calculated from observable Thiele modulus reflected the dependence of K_M on geometrical parameters of the particles. A new method for determination of the overall intraparticle pH was developed based on luminescence lifetime measurements in the frequency domain. Sepabeads were doubly labeled using a lipophilic variant of the pH‐sensitive dye fluorescein, and Ru(II) tris(4,7‐diphenyl‐1,10‐phenantroline) whose phosphorescence properties are independent of pH. Luminescent lifetime measurements of doubly labeled particle suspensions showed superior signal‐to‐noise ratio compared to fluorescence intensity‐based measurements using singly labeled particles. The difference at apparent steady state (ΔpH) between bulk (external pH) and intraparticle pH (internal pH) was as large as ～0.6 units. The ΔpH was dependent on substrate concentration, particle size, and pore diameter. Therefore, these results characterize the role of carrier characteristics and reaction parameters in the formation of concentration gradients for substrate and acidic product during hydrolysis of cephalosporin C by immobilized amidase. The strong pH dependence of the immobilized amidase underscores the importance of considering intraparticle pH gradients in the design of an efficient carrier‐bound biocatalyst. Biotechnol. Bioeng. 2010;106: 528–540. © 2010 Wiley Periodicals, Inc.