Soybean-milk-coagulating activity of Bacillus pumilus derives from a serine proteinase.

A proteolytic enzyme from Bacillus pumilus strain TYO-67, which was able to coagulate the protein in soybean milk, was characterized enzymologically. The optimum pH and temperature for its activities were 9.0 and 50 degrees C, respectively. The enzyme was strongly believed to be a serine proteinase because it was completely inhibited by the addition of diisopropyl fluorophosphate or phenylmethanesulfonyl fluoride. Hammerstein milk casein, cytochrome c and soybean protein were good substrates for the enzyme. Seven cleavages were detected using the oxidized insulin B-chain as peptide substrate for the proteolytic specificity test of the serine proteinase from B. pumilus. The bonds most susceptible to the action of the serine proteinase from B. pumilus were Leu-15-Tyr-16. The mode of action on soybean milk protein by the enzyme from B. pumilus was also investigated. The acidic subunit in glycinin and the alpha-, alpha- and beta-subunits in beta-conglycinin were degraded during the enzyme reaction. However, the basic subunit in glycinin could not be degraded by the enzyme. The formation of coagula in soybean milk caused by the serine proteinase from B. pumilus was mainly due to the hydrophobic interaction.

Purification and characterization of a soybean-milk-coagulating enzyme from Bacillus pumilus TYO-67.

Bacillus pumilus TYO-67 was isolated from tofu (soybean curd) as the best producer of a soybean-milk-coagulating enzyme, induced by the addition of soybean protein to the growth medium. The enzyme was purified approximately 30-fold with an 11% yield. The homogeneous preparation of the enzyme showed that it is a monomer with a molecular mass of about 30 kDa and has an isoelectric point at pH 9.75. The results of amino acid composition analyses showed that the enzyme is rich in alanine, aspartic acid, glycine, serine and valine. Although the amino-terminal amino acid (alanine) was identical with that of subtilisins, the amino-terminal sequence was different from those of subtilisins. The alpha-helix content of the enzyme was calculated to be 28.2%. The optimum pH and temperature were observed at 6.0-6.1 and 65 degrees C respectively. The enzyme was significantly activated by the addition of 1 mM Mn2+, Ca2+, Mg2+, and Sr2+ ions in the reaction mixture, and its thermal stability was significantly increased by Ca2+ ion.

Synthesis and Fungicidal Activity of 6-Alkyl Six-membered Cyclic Thiophosphates.

Synthesis and fungicidal activities of new 6-aIkyl six-membered cyclic phosphates were examined. Ten kinds of 6-alkyl six-membered cyclic thiophosphates were synthesized by reaction with 5-alkyl-2-hydroxybenzyl alcohols and phosphoric agents. Among the prepared compounds, 2-ethoxy-6-elhyl-4H-1,3,2-benzodioxaphosphorin 2-sulfide (1) had activity as potent as the commercial fungicide iprobenfos against Pythium sp. and Corticium rolfsii at 10ppm.

Syntheses and biological activities of dihydro-5,6-dehydrokawain derivatives.

The syntheses and biological activities of dihydro-5,6-dehydrokawain derivatives against plant pathogenic fungi and termites were investigated. Dihydro-5,6-dehydrokawain was isolated by a simple method without chromatography from the leaves of Alpinia speciosa K. SCHUM. The white crystalline compound obtained was identified as dihydro-5,6-dehydrokawain (1) by instrumental analyses. 4-Hydroxy-6-(2-phenylethyl)-2H-pyran-2-one (3) was prepared by hydrolyzing dihydro-5,6-dehydrokawain. Three dihydro-5,6-dehydrokawain derivatives were synthesized by reacting 3 with phosphoric agents. Among the synthesized compounds, dimethyl [6-(2-phenylethyl)-2-oxo-2H-pyran-4-yl]phosphorothionate (4) had the strongest antifungal activity of 91% at 100 ppm against Corticium rolfsii.

Synthesis and antifungal activity of cinnamic acid esters.

Cinnamic, p-coumaric and ferulic acids were isolated from pineapple stems (Ananas comosus var. Cayenne). Twenty-four kinds of esters were prepared from these acids, alcohols and the components of Alpinia. Isopropyl 4-hydroxycinnamate (11) and butyl 4-hydroxycinnamate (12) were found to have almost the same effectiveness in antifungal activity against Pythium sp. at 10 ppm as that of the commercial fungicide iprobenfos (kitazin P).