13C-NMR Spectra and Streochemistry of Isoechinulins A,B and C

¹³C-NMR spectra of isoechinulins A, B and C, metabolites from Aspergillus ruber, were fully assigned on the basis of chemical shifts and multiplicities and comparison with their analogues. Taking advantage of the symmetrical structure of the diketopiperazine ring, the stereochemistry of the trisubstituted carbon-carbon double bond in a dehydrotryptophyl moiety was determined as Z (cis) by measuring the coupling constants, , in the proton nondecoupled spectrum of isoechinulin B.     

X-Ray Crystal Structure of Pyrenocine A,a Phytotoxin from Pyrenochaeta terrestris

The milk fat globule membrane (MFGM) enclosing fat droplets in bovine milk was isolated, and its effects on hydrolysis of milk fat by lipases were investigated by using a gum arabic-stabilized milk fat emulsion as substrate. The addition of isolated MFGM to the reaction mixture markedly inhibited hydrolysis by pancreatic and microbial (Rhizopus delemer) lipases. The inhibition was completely lost on tryptic digestion of MFGM, suggesting that the protein moiety of MFGM played a role in the inhibition. Soluble glycoprotein (SGP) which was isolated from delipidated MFGM produced marked inhibitory activity. The inhibition by SGP was dependent on substrate concentration, suggesting that the inhibition was at least partly due to coverage and blockage of the substrate surface by SGP.     

Isolation and Identification of a Sexual Hormone in Yeast

5-Fluorotryptophan (5FT), indolmycin (IM), 4-fluorotryptophan and 7-azatryptophan were found on screening to be tryptophan antagonists among various chemically synthesized and naturally occurring tryptophan analogues for the isolation of l-tryptophan (l-Trp) producing mutants of Bacillus subtilis K.

From among 5FT resistant mutants, potent l-Trp producers were obtained using an improved isolation medium. Growth of the isolated 5FT-resistant l-Trp producer, AJ 11709, was inhibited by IM. From among 5FT and IM resistant mutants, the best strain, AJ 11979, which produced 9.0 g/liter of l-Trp from 13% glucose on 120hr cultivation, was selected.     

Some Properties and Characterization of Rice Seed Hemagglutinin

The phytohemagglutinin of rice seed has been purified by a sequence of steps involving fractionation with ammonium sulfate and successive chromatography on DEAE-and eMcellulose and finally gel filtration on Bio-Gel P-100. The purified rice seed hemagglutinin was shown to be homogeneous by electrophoresis on polyacrylamide gel and its molecular weight was 10,000, calculated from both the Ve/Vo value of gel filtration on Bio-Gel P-100 and the sum of the individual constituents (amino acids, sugars and metals). In addition to amino acid, the rice seed hemagglutinin contained 26.8% covalently bound carbohydrate which was identified and quantitated by gas chromatography of the acetylated alditols. Glucose was the predominant sugar with lesser amounts of glucosamine, xylose, and mannose also being present. And the rice seed hemagglutinin contained 1 g atom of calcium per molecule. The molecular weight of the rice seed hemagglutinin is smallest compared with some of phytohemagglutinins isolated from leguminous seeds and other plant sources. The rice seed hemagglutinin has the blastogenetic activity for human peripheral lymphocytes as well as Phaseolus vulgaris phytohemagglutinins or concanavalin A, jack bean hemagglutinin.     

Gibberellins in Immature Seeds of Pharbitis nil

A new gibberellin, gibberellin A₂₀ (GA₂₀), was isolated from immature seeds of morning-glory (Pharbitis nil). Its structure was established as 4aα, 7α-dihydroxy-1β-methyl-8-methylenegibbane-1α, 10β-dicarboxylic acid-1→4a lactone (I) on the basis of its physicochemical analysis as well as chemical evidences. GA₂₀ shows marked growth promoting activities on dwarf maize d₂ and d₅ but weak activities on d₁, rice seedling and dwarf pea.     

Partial Purification and Some Properties of ADP-glucose Phosphorylase from Potato Tubers

ADP-glucose phosphorylase [adenosine diphosphate glucose: orthophosphate adenyl- yltransferase; Dankert et ah, Biochim. Biophys. Acta, 81, 78 (1964)] was found to be widely distributed in plant tissues. The enzyme was purified 570-fold in a 24% yield from cell- free extract of growing tubers of potato (Solanum tuberosum L.). The following reaction catalyzed by the purified enzyme was found to proceed stoichiometrically. ADP-glucose +P₁→ADP+glucose-1-P

Maximal activity was observed at pH 8. The enzyme was the most stable at pH 7, showing 50% loss of its original activity after 50 min heating at 57°C. The following kinetic parameters were obtained: activation energy, 11.1 kcal/mole; Km (P₁), 2.5 mm; Km (ADP-glucose), 0.05 mm. The enzyme did not act on GDP-mannose, GDP-glucose and UDP-glucose. Neither activator nor inhibitor was found among various phosphorylated metabolites tested. The enzyme was inhibited by metal-binding reagents, EDTA and o-phenanthroline. None of the metal ions tested was found to recover the activity of chelator-treated enzyme.     

Occurrence of Castasterone,Brassinolide and Methyl 4-Chloroindole- 3-acetate in Immature Vicia faba Seeds

The rice lamina inclination test indicated the presence of brassinosteroid-like active substances in immature Vicia faba seeds. Two of these were identified as castasterone and brassinolide by GC/MS and GC/SIM, respectively. Another active principle was identified as methyl 4- chloroindole-3-acetate by GC/MS and HPLC.     

Regulatory Properties of Sucrose Synthetase in Sweet Potato Roots

The molecular weight of the yeast tannase [E.C. 3.1.1.20, tannin acyl-hydrolase] of Candida sp. was determined to be 250,000 by gel filtration on Sephadex G–200. The enzyme was dissociable into two identical subunits with molecular weight of 120,000 on SDS-polyacrylamide gel electrophoresis. The amino acid analysis revealed that the enzyme consisted of 786 amino acid residues per protein molecule. The polypeptide moiety of the enzyme was 38 % by the Lowry-Folin reaction and 35% by the amino acid analysis. The enzyme contained 62% neutral sugars, which were identified as mannose and galactose on cellulose thin-layer chromatogram and 2.2 % hexosamines.     

Purification and Properties of an S-PI(Pepstatin Ac)-insensitive Carboxyl Proteinase from a Xanthomonas sp. Bacterium

A S-PI(Pepstatin Ac)-insensitive carboxyl proteinase was found in culture filtrate of a Xanthomonas sp. bacterium. The carboxyl proteinase was highly purified and about 100 mg of the enzyme was obtained from 601 of culture filtrate, with a recovery of 25%. The optimum condition for the action of the purified enzyme toward casein was approx. pH 2.7 and its activity was not inhibited by any of such carboxyl proteinase inhibitors as Pepstatin, S-PI, and DAN but EPNP inhibited it. Such behavior of the enzyme against inhibitors resembles that of Pseudomonas sp. carboxyl proteinase, the first found from a bacterium. Some differences were observed, however, in their properties such as optimum pH, isoelectric point, and amino acid composition.     

Structures of Allosamidins,Novel Insect Chitinase Inhibitors,Produced by Actinomycetes

The structures of allosamidin (1) and methylallosamidin (2), novel insect chitinase inhibitors, were elucidated as 1 and 2 by acid hydrolysis experiments and analyses of 2d-NMR spectra. They are unique basic pseudotrisaccharides consisting of 2-acetamido-2-deoxy-d-allose (N-acetyl-d- allosamine) and a novel aminocyclitol derivative (3), termed allosamizoline.