Kazuo Miyairi

Antifungal Cyclodepsipeptides, W493 A and B, from Fusarium sp.: Isolation and Structural Determination

W493 A and B, which showed strong antifungal activity, were isolated from a culture broth of Fusarium sp. The structure of W493 B was determined to be that of a cyclodepsipeptide, cyclo(3S,4R-HMTA-D-allo-Thr-L-Ala-D-Ala-L-Gln-D-Tyr-L-Ile) (1) by MS and NMR data, an amino acid analysis, and synthesis of the component. HMTA represents 3-hydroxy-4-methyltetradecanoic acid. W493 A (2) had a similar structure, except that L-Ile in 1 was replaced by L-Val. The absolute configuration of each amino acid was determined by chiral HPLC, and the sequence of the components was determined by HMBC experiments. The sequence of the two alanines was determined to be a L-Ala-D-Ala by a chiral HPLC analysis of the peptide fragment containing only one Ala residue. The absolute configuration of HMTA obtained from the hydrolysis of W493 B was determined to be 3S and 4R by comparing with four isomers prepared by enantioselective synthesis via Sharpless asymmetric epoxidation.

Expression, purification, and analyses of glycosylation and disulfide bonds of Stereum purpureum endopolygalacturonase I in Pichia pastoris.

We have succeeded in the expression of Stereum purpureum endopolygalacturonase I (EndoPG I) using the Pichia expression system and in purification of the three kinds of recombinant EndoPG I, which have one to three sugar chains by using CM52 column chromatography. The sugar chains which were added to EndoPG I were the M8, M9, and/or M10 high-mannose type. The results of LC-MS analysis showed that recombinant EndoPG Is were randomly glycosylated at four N-glycosylation sites. From the thermal denaturation curves of the recombinant enzymes, it was suggested that EndoPG I differing in thermal stability was included in the sample after purification. Therefore, we investigated the disulfide bonds of recombinant EndoPG I by LC-MS analysis. As a result, peptides without a second or third disulfide bond were detected. This result is the first indicating that there are incomplete enzymes in terms of disulfide bonds in the Pichia expression system.

Crystallization and preliminary X-ray study of endopolygalacturonase from the pathogenic fungus Stereum purpureum

Crystals of endopolygalacturonase I from Stereum purpureum have been obtained by the vapour-diffusion method. Prior to crystallization work, endopolygalacturonase I was deglycosylated with endo-beta-N-acetylglucosaminidase H. The crystal diffracts to ultrahigh (0.96 A) resolution using synchrotron radiation and belongs to space group P1, with unit-cell parameters a = 37.26, b = 46.34, c = 52.05 A, alpha = 67.17, beta = 72.44, gamma = 68.90 degrees.

Characterization of an endopolygalacturonase Gene cppg1 from Phytopathogenic Fungus Chondrostereum purpureum

Chondrostereum purpureum,a phytopathogenic fungus, produces endopolygalacturonase (endoPG) which has been suggested to have a causal role in the silver-leaf symptom of apple trees. In this paper, we detected C. purpureurn-derived endoPG at the infection sites using ELISA with a polyclonal antibody against endoPG I. A gene encoding endoPG I and its homolog were also isolated from the C. purpureum genome. The endoPG I gene was designated as cppg1. The cppg1 gene is the first fungal endoPG gene reported in the Basidiomycetes.

Cloning of the Gene Encoding an Endo-Acting Pectate Lyase from Streptomyces thermocarboxydus

An endo-acting family 3 pectate lyase (PL I) gene from Streptomyces thermocarboxydus was cloned and expressed in Escherichia coli. The deduced PL I sequence had highest similarity to a putative pectate lyase of S. coelicolor. Recombinant PL I had significantly lower specific activity, probably a result of incorrect folding, as indicated by circular dichroism spectra analysis.

α-Selective glycosylation with 5-thioglucopyranosyl donors; synthesis of an isomaltotetraoside mimic composed of 5-thioglucopyranose units

A general method for alpha-selective glycosylation with 5-thioglucopyranosyl donors followed by efficient deprotection of the resulting products was developed. This methodology was utilized in the synthesis of an isomaltotetraoside analogue.

Synthesis of D-Trigalacturonic Acid Methylglycoside and Conformational Comparison with Its Sulfur Analogue

D-Trigalacturonic acid methylglycoside (3) was synthesized to evaluate the previously synthesized sulfur analogue 1 by comparison. The NOE experiments revealed that both 3 and 1 took on a similar conformation around their glycosyl linkage.

S-RNases from self-incompatible and -compatible apple cultivars: purification, cloning, enzymic properties, and pollen tube growth inhibitory activity.

Four S-RNases (RNase associated with self-incompatibility) were purified from the styles of two apple cultivars (Malus domestica), a self-incompatible cv., Starking Delicious (SD), and a self-compatible cv., Megumi (MG). Each cultivar produced two S-RNases and their enzymatic properties such as specific activity, pH optimum, thermal stability, and molecular mass, were characterized. The four S-RNases inhibited the tube growth of apple pollen in an in vitro bioassay at 25 μg/ml (1.0 μM), but did not distinguish self from non-self pollen. The cDNAs of four S-RNases were cloned, and the nucleotide and deduced amino acid sequences were analyzed. The nucleotide sequence of SD-Se RNase was a new one and the other was identical to that of Sc-RNase of cv. Fuji. In MG one was identical to the sequence of SD-Sc RNase and the other to that of Sa-RNase of cv. Golden Delicious except for one base. From results of the isolation amounts and the Western blot analysis for stylar crude extracts the amount of S-RNases in MG was apparently less than that in SD.

Synthesis of a trigalacturonic acid analogue mimicking the expected transition state in the glycosidases

A trigalacturonic acid analogue carrying a cyclohexene framework in place of the central pyranose ring was synthesized as a molecular probe for the mechanistic investigation of endo-polygalacturonase 1 (endo-PG 1). Preliminary enzymatic studies revealed that this analogue inhibited endo-PG 1 activity by about 30% at 0.3mM concentration.

The Pro-Form of Stereum purpureum Endopolygalacturonase I Is Inactivated by a Pro-Sequence in the C-Terminal Region

The Pro-form (Pro-EndoPG I) of Stereum purpureum endopolygalacturonase I has a unique C-terminal region (pro-sequence) that is lacking in PGs of other origins. Mature EndoPG I purified from the culture filtrate of this fungus does not have the 44-amino-acid pro-sequence present in Pro-EndoPG I. We expressed Pro-EndoPG I in Escherichia coli and examined its activity. It was found that Pro-EndoPG I had no PG activity, but that PG activity was acquired after the degradation of part of the pro-sequence with V8 protease. These results suggest that the pro-sequence inactivates auto-PG activity. No similar characteristic has been reported for any glycoside hydrolase. We then constructed EndoPG I mutants and identified two Glu residues, E364 and E366, that were related to auto-inactivation. A test involving injection of the enzyme into apple trees showed that Pro-EndoPG I induced the same silver-leaf symptoms as mature EndoPG I.