Further Investigation on Naturally Occurring Tocopherols and Tocotrienols in Bovine Milk Fat

The polar lipid material which contains most of unsaponiriable matter of milk fat was collected by means of neutral alumina column chromatography. After saponification of the polar lipid material, the unsaponiriable matter was purified by repeated Florisil and neutral alumina column chromatography and the total tocopherol fraction was obtained. It was found that the total tocopherol fraction isolated from milk fat contained 6 of the known naturally occurring tocopherols, that is, α-, β-, γ-, and δ-tocopherols and α- and γ-tocotrienols. These were identified by two-dimensional thin-layer and gas-liquid chromatography before and after hydrogenation.     

recE-Dependent Gene Amplification Induced by a Tunicamycin-resistant Mutation (tmr A7) in Bacillus subtilis

A recombinant Bacillus subtilis phage, ρ11-AA248, contains the tmr A7-amy R2-amy E⁺-tmr B⁺-aroI⁺ region of the B. subtilis N7 chromosome on a 22.4 kb DNA fragment. The amy E⁺-tmr B⁺ gene region in the phage genome of the B. subtilis 207-21 transductants by ρ11-AA248 was amplified to approximately 10 copies after cultivation in the presence of tunicamycin (10 μg/ml) and to two copies without tunicamycin. The amplification of the gene region caused hyper-production of extracellular α-amylase. In contrast, no amplification of the gene region was detected in the transductants of B. subtilis 207-25, a recE-deficient derivative of 207-21 strain.     

The Adsorption of Whey Proteins on the Surface of Emulsified Fat

Whey proteins adsorbed on fat globule surfaces during emulsification with coconut oil at pH 3 ~ 9 were examined. The amount of proteins adsorbed on the fat surface was dependent on the pH during emulsification. At any pH examined here, however, tightly-adsorbed proteins which were not extracted from the fat surface with urea or guanidine-HCl were 2 ~ 3 mg/m². Marked selectivities in the adsorption of individual whey proteins were observed at any pH. No correlation between the adsorbabilities and the surface hydrophobicities of individual whey proteins was observed. Whey proteins adsorbed on the emulsified fat were much more easily digested with proteases compared to the native whey proteins, indicating that conformational changes of whey proteins occurred at the fat surface. The results suggested that conformational properties, such as flexibility of the structure, of whey proteins are important in the adsorption and possibly affect their emulsifying ability.     

Effect of Pepsin Inhibitor (S-PI) on the Growth of Rhodotorula glutinis No. K-24

A tissue-type transglutaminase (TGase) was purified from liver tissue of the red sea bream, Pagrus major, by ion-exchange chromatography and heparin-Sepharose affinity chromatography. Its activity was assessed using a fluorometric assay to measure the incorporation of monodansylcadaverine into N,N′-dimethyl casein. The molecular mass of purified TGase was estimated to be 78kDa by SDS–polyacrylamide gel electrophoresis. The enzyme required Ca²⁺ to express its activity, although 10 mM Sr²⁺ also activated the enzyme fully. TGase activity was maximal at pH 9.0–9.5, and the enzyme was strongly inhibited by sulfhydryl reagents. The purified enzyme catalyzed the cross-linking of myosin heavy chain obtained from Alaska pollack, resulting in gelation of an actomyosin solution. The partial amino acid sequence of this fish TGase showed divisionally significant similarity to TGase from guinea pig liver.     

Isolation and Identification of γ-l-Glutamyl-l-glutamic Acid from Tobacco Cells in Suspension Culture

The Maillard Reaction (MR) rate below the glass transition temperature (T_g) for various model glassy food systems was studied at temperatures between 40 °C and 70 °C. As a sample, freeze-dried glucose and lysine systems embedded in various glassy matrices (e.g., polyvinylpyrrolodone and trehalose) were used, and the MR rate below the T_g was compared among the various glassy matrices. The extent of MR was estimated spectrophotometrically from the optical density at 280 nm (OD₂₈₀), and the MR rate (k₂₈₀) was determined as a pseudo zero order reaction rate from the time course of OD₂₈₀. Although k₂₈₀ was described by the Arrhenius plot, the temperature dependence of k₂₈₀ was almost the same and the intercept was different among the matrices. From the comparison of k₂₈₀, it was suggested that the MR rate in glassy matrix was affected not only by the T_g, but also by the hydrogen bonding between MR reactants and glassy matrix.     

Galactan Isolated from the Midrib of the Leaves of Nicotiana tabacum

The structure of a galactan, obtained from the pectic polysaccharides of the midrib of the leaves of Nicotiana tabacum, was investigated by methylation analysis and partial acid hydrolysis. The galactan contained only d-galactose and was composed of a straight chain of β-(1→4)-linked d-galactopyranosyl residues.     

Studies on Tobacco Lignin

A study was made of such characteristics as infrared and ultraviolet absorption spectra, alkaline nitrobenzene oxidation, elementary composition and constituent groups of tobacco milled wood lignin (Japanese flue-cured and Matsukawa M. W. L.).

Methoxyl contents of mid-rib and stalk M. W. L. were 12.3~13.8% and 16.6~17.0% respectively. Infrared absorption spectra showed that the relation of the absorption intensities between at 1270 cm^?1 and at 1220 cm^?1 of stalk M. W. L. was 1270 cm^?1 < 1220 cm^?1 but, on the contrary, in the case of mid-rib M. W. L., the relation of the intensities was 1270 cm^?1 = 1220 cm^?1. Alkaline nitrobenzene oxidation indicated that the nuclear structures of tobacco M. W. L. were mainly composed of p-hydroxyphenyI and guaiacyl for mid-rib, and the former two and syringyl for stalk.     

Purification and Properties of an Exocellular γ-Glutamyl Arylamidase from Bacillus sp. Strain No. 12

An exocellular γ-glutamyl arylamide-hydrolyzing enzyme was produced by a Bacillus sp. in L-glutamate-containing medium. This enzyme was a tetrameric simple protein composed of two heavy subunits (Mr 56,000) and two light subunits (Mr 46,000). It hydrolyzed γ-amido, acyl and aryl bonds in L- and D-glutamyl compounds, and the activity on L-glutamic acid γ-p-nitroanilide was inhibited by the addition of glutamate and γ-glutamyl compounds but not by α-glutamyl compounds. The activity was stimulated by various dipeptides but not by free amino acids, L-Alanine, glycine, L-serine and L-cysteine inhibited the enzyme competitively. Addition of hy-droxylamine had no effect on the activity.     

Emulsifying Properties of a Mixture of Peptides Derived from the Enzymatic Hydrolyzates of Bovine Caseins

β-CN(f193–209), a hydrophobic peptide of 17 residues obtained from the chymosin hydrolyzate of β-casein, had little emulsifying activity (EA) at a neutral pH. When mixed with a hydrophilic glycomacropeptide (GMP) derived from κ-casein however, the EA of β-CN(f193-209) increased greatly. The mixing ratio of the peptides affected the EA as well as the adsorption of the peptides to oil droplets. Scanning electron microscopy indicated that the peptide film surrounding the emulsified oil droplets was thick and rough compared to the protein film. An amphipathic structure formed by some interaction between the hydrophilic GMP and the hydrophobic β-CN(f193-209) might contribute to the formation of the thick peptide film and stabilize the emulsified oil.     

Characterization of Plasma Membrane Proteins from Lactating Bovine Mammary Gland

Properties of proteins in the light (<d 1.03 on Ficoll and then <d 1.14 on sucrose) and heavy (d 1.03/1.05 on Ficoll and then <d 1.14 on sucrose) plasma membranes (PM) isolated from lactating bovine mammary gland were investigated. The PMs consisted of 57 ~ 62% of protein and 38 ~ 43% lipid. The lipid/protein ratio was 0.77 in the light PM and higher than 0.61 of the heavy PM. However, no appreciable differences were found between the light and heavy PMs with respect to polypeptide, amino acid, and carbohydrate compositions. The protein moiety contained approximate 5 ~ 6% carbohydrate: fucose 8 ~ 9, mannose 11 ~ 12, galactose 16, N-acetylglucosamine 32,N-acetylgalactosamine 12 ~ 15, and sialic acid 17~20 mol%. PM protein was high in the content of aspartic acid, glutamic acid, and leucine and low in proline, cystine, methionine, and histidine. On double immunodiffusion both PMs formed precipitin lines against milk fat globule membrane (MFGM) antiserum. Electrophoretic analysis on sodium dodecyl sulfate-polyacrylamide gel revealed the presence of many minor polypeptides and three major glycopeptides (PAS-I, II, and III) of molecular weights of 115,000, 94,000, and 82,000. The glycoprotein profiles of the PMs were different from those of MFGM, except that PAS-II and -III of PM corresponded to PAS-3 and -4 of MFGM, respectively.