Isolation and Characterization of a Prolidase from Streptococcus cremoris H61

A prolidase with a molecular weight of 43,000 was purified to homogeneity from a cell-free extract of Streptococcus cremoris H61. The optimum pH of the enzyme was in the range of 6.5 to 7.5. The hydrolyzing activity was specific for dipeptides of the X-Pro type. Kinetic constants for 4 dipeptides (Leu-Pro, Phe-Pro, Val-Pro and Ala-Pro) were estimated. Km values were not very different for these substrates, but V_max values were quite different (Leu-Pro > Phe-Pro, Val-Pro > Ala-Pro). The enzyme was activated by cobalt ion and inactivated by metal-chelating agents or with 2-mercaptoethanol.     

Synthesis of Maltosyl(α1→6)cyclodextrins through the Reverse Reaction of Thermostable Bacillus acidopullulyticus Pullulanase

Maltosyl(α1→6)α-, β or γ-cyclodextrin was synthesized from maltose and α-, β- or γ- cyclodextrin, respectively, using Bacillus acidopullulyticus pullulanase (EC 3.2.1.41). More than 40% of each cyclodextrin substrate was converted to the corresponding maltosyl(α1→6)cyclodextrin under the conditions given below; the combined concentration of maltose and cyclodextrin was 70 ~ 75 % (w/w), the molar ratio of maltose to cyclodextrin was 9~18, and the amount of pullulanase was 100~200units/g of cyclodextrin. The optimum pH and temperature for the formation of maltosyl(α1→6)cyclodextrins were 4.0—4.5 and 60~70°C, respectively. Each maltosyl(α1→6)-cyclodextrin produced was separated from noncyclic saccharides, maltose and branched tetraose, by methanol and ethanol precipitations. The maltosyl(α1→6)cyclodextrins were further purified by gel filtration on a Toyopearl HW 40 S column and crystallization from aqueous (for maltosyl(α1→6)β-cyclodextrin) or methanol (for maltosyl(α1→6)β-cyclodextrin) solution. From 10 g each of the corresponding cyclodextrin, the yields of the purified maltosyl(α1→6)α-, β- and γ-cylcodextrins were 3.0 ~ 3.6 g, 2.5 ~ 2.8g and 2.2 ~ 2.5 g, respectively. Identification of the maltosyl(α1-6)cyclo-dextrins was performed by means of hydrolysis with Klebsiella pneumoniae pullulanase, methyla- tion analysis and ¹³C-NMR analysis.     

Comparison of Four Distinct Idiotypes of Monoclonal Antibodies against Hen’s Egg Ovomucoid

Two monoclonal antibodies (mAb 41B3 and mAb 51B3), directed against hen’s egg ovomucoid (OM) and different from those we previously reported (mAb 23E5 and mAb 32A8), were prepared and purified. A competitive radioimmunoassay using ¹²⁵I-labeled OM showed that both mAb 41B3 and mAb 51B3 could bind all three homologous domains (domains I (DI), II (DII) and III (Dili)) of OM and that they reacted most efficiently with Dill. To analyze the paratope specificities of these four mAbs, a sandwich assay and a competitive radioimmunoassay were done. Only the pair mAb 41B3 and mAb 51B3 could not simultaneously bind the OM or domains in the sandwich assay. Only mAb 41B3 inhibited the binding of mAb 51B3 to antigens and vice versa in the competitive radioimmunoassay. These results suggest that mAb 41B3 and mAb 51B3 recognized a closely related site distinct from the epitopes for mAb 23E5 or mAb 32A8. These mAbs may be useful for general studies on epitopes of protein antigens as well as for analyses of the antigenic determinants of OM.     

Synthesis and Biological Activity of the Lipophilic Derivatives of N- Acetyl-1-thiomuramoyl-l-alanyl-d-isoglutamine

A variety of the lipophilic derivatives at C-1 and C-6 in N-[2-O-(2-acetamido-2,3-dideoxy-1-thio-β-d-glucopyranose-B-yl)-d-lactoy]-l-alanyl-(N¹-fatty acyl)-d-isoglutamine methyl esters were synthesized from 2N-acetyl-1-S-acetyl-4,6-O-isopropylidene-1-thiomuramoyl-l-alanyl-d-isogluta-mine methyl ester. Their immunoadjuvant activity in guinea-pigs, and the protective effect in mice infected with Escherichia coli (E-77156) were examined.     

Development of New Zinc Dithiosemicarbazone Complex for Use as Oral Antidiabetic Agent

The increasing prevalence of diabetes mellitus (DM) worldwide has underscored the urgency of developing an efficient therapeutic agent. Recently, Zn complexes have been attracting attention due to their antidiabetic activity. In this study, we designed and synthesized a new Zn complex, Zn-3,4-heptanedione-bis(N ⁴-methylthiosemicarbazonato) (Zn-HTSM), characterized its physicochemical properties, and examined its antidiabetic activity in KK-A^y type 2 DM model mice. It was demonstrated that Zn-HTSM has adequate lipophilicity for the cellular permeability, shows potent hypoglycemic activity, and improves glucose intolerance in KK-A^y mice. We also analyzed the levels of serum adipokines after continuous oral administration of Zn-HTSM. The level of serum leptin of KK-A^y mice is significantly reduced by the treatment of Zn-HTSM. Nevertheless, the levels of serum insulin and adiponectin were not improved. These data suggested that the Zn-HTSM acts on the leptin metabolism. Our present studies indicate that Zn-HTSM is a candidate oral antidiabetic agent for the treatment of type 2 DM.     

Development of recombinant chicken IgY from single chain fragment of variable region for diagnosis of BSE.

We generated two recombinant chicken IgYs, designated Ab3-15 and Ab4-19, against mammalian prion protein (PrP) from the single chain fragment of variable region (scFv) antibodies. These two antibodies recognized PrP(Sc) from bovine spongiform encephalopathy (BSE) in cattle and were more sensitive than the corresponding scFv antibodies. These antibodies also recognized PrP(Sc) from other scrapie-infected mammals. These results indicate that Ab3-15 and Ab4-19 are useful for diagnosis of BSE as well as other prion diseases.     

An integrated-likelihood method for estimating genetic differentiation between populations

The aim of this article is to develop an integrated-likelihood (IL) approach to estimate the genetic differentiation between populations. The conventional maximum-likelihood (ML) and pseudolikelihood (PL) methods that use sample counts of alleles may cause severe underestimations of FST, which means overestimations of theta=4Nm, when the number of sampling localities is small. To reduce such bias in the estimation of genetic differentiation, we propose an IL method in which the mean allele frequencies over populations are regarded as nuisance parameters and are eliminated by integration. To maximize the IL function, we have developed two algorithms, a Monte Carlo EM algorithm and a Laplace approximation. Our simulation studies show that the method proposed here outperforms the conventional ML and PL methods in terms of unbiasedness and precision. The IL method was applied to real data for Pacific herring and African elephants.