Chemical change involved in the oxidative reductive depolymerization of hyaluronic acid

The oxidative reductive depolymerization (ORD) of hyaluronate has been investigated. A solution of hyaluronate (Mr 4.07 x 10(5] in phosphate buffer (pH 7.2) was incubated in the presence of Fe2+ for 24 h at 37 degrees C under an oxygen atmosphere to yield depolymerized hyaluronate (ORD fragments; an average Mr of 2,600). The ORD fragments contain 21 and 24% less hexosamine and uronic acid, respectively, but no olefinic linkage. They were exhaustively digested with chondroitinase AC-II. The resulting oligosaccharides and monosaccharides were separated by gel filtration and ion-exchange chromatography, and their structures were determined by proton and carbon-13 NMR, fast atom bombardment mass spectrometry, and chromatographic techniques combined with chemical modifications. The following structures derived from the reducing ends of the ORD fragments were identified: 4,5-unsaturated GlcA(beta 1----3)-N-acetyl-D-glucosaminic acid (where GlcA- represents glucuronosyl-) (21%), 4,5-unsaturated GlcA(beta 1----3)GlcNAc(beta 1----3)-D-arabo-pentauronic acid (24%), and N-acetyl-D-glucosamine (51%). The following structures derived from the nonreducing ends were identified: L-threo-tetro-dialdosyl-(1----3)GlcNAc (a tentative structure, 8%), N-acetylhyalobiuronic acid (20%), and N-acetyl-D-glucosamine (45%). The results indicate that the ORD reaction of hyaluronate proceeds essentially by random destruction of unit monosaccharides due to oxygen-derived free radicals, followed by secondary hydrolytic cleavage of the resulting unstable glycosidic substituents.     

Developmental Changes in the Bombyxin-and Insulin-like Immunoreactive Neurosecretory System in the Wax Moth, Galleria mellonella

Four medial neurosecretory cells (MNC) and 4 lateral neurosecretory cells (LNC) in each brain hemisphere, and one pair of cells in each thoracic ganglion (TG) of Galleria larva react with antibodies against bombyxin and insulin. Material secreted from the MNC and LNC is released mainly in the corpora allata, and that from the TG through the ventral median nerves. Intrinsic secretory cells of the corpora cardiaca (CC) also contain bombyxin-like, but not insulin-like material. The immunoreactivities all disappear during molts and reappear with resumption of feeding. In the MNC and TG they reappear for less than a day, but in cells of the CC immunoreactivity reappears for the whole feeding period. Before pupation, the LNC become temporarily immunopositive towards the end of feeding period, and the MNC and TG during the wandering period, i.e. at the time of prothoracic gland stimulation. Immunoreactivity disappears during the pupal molt. In pupae it is present in the 4 pairs of MNC and 1–2 pairs of LNC 12–48 hr after ecdysis, and in cells of the CC from 12 hr after ecdysis until the end of the pupal instar. In adult, immunoreactivity is restricted to 2 pairs of the LNC and to CC cells.     

Synthesis of D-cysteine from 3-chloro-D-alanine and hydrogen sulfide by 3-chloro-D-alanine hydrogen chloride-lyase (deaminating) of Pseudomonasputida

Synthesis of D-cysteine from 3-chloro-D-alanine and hydrogen sulfide is catalyzed by highly purified 3-chloro-D-alanine hydrogen chloride-lyase from $\text{Pseudomonas}\text{putida}$. The synthetic reaction proceeds optimally at pH 8.5, as a function of enzyme concentration and incubation time. The enzymatically synthesized D-cysteine was isolated from the large scale reaction mixture and identified by physicochemical means.     

Catalytic activity and arrangement of subunit polypeptides in rat liver cytochrome c oxidase as studied by proteolysis

Cytochrome c oxidase from rat liver was incubated with various proteinases of different specificities and the enzymic activity was measured after various incubation times. A loss of catalytic activity was found after digestion with proteinase K, aminopeptidase M and a mitochondrial proteinase from rat liver. In each case the decrease in enzymic activity was compared with the changes in intensities of the polypeptide pattern obtained after sodium dodecyl sulfate polyacrylamide gel electrophoresis. The susceptibilities of the subunit polypeptides of the soluble cytochrome c oxidase to proteinases were very different. Whereas subunit I was most susceptible, subunits V–VII were rather resistant to degradation. From the relative inaccessibility of subunits V–VII to proteinases it is likely that these polypeptides are buried in the interior of the enzyme complex.     

Peptide inhibitors of angiotensin I-converting enzyme in digests of gelatin by bacterial collagenase.

Peptide inhibitors of angiotensin I-converting enzyme (peptidyldipeptide hydrolase, EC 3.4.15.1) were produced by digesting gelatin with bacterial collagenase. The inhibitors were isolated from the digests with a combination of alcohol fractionation, treatment with Amberlite CG-50 column, gel filtration through Sephadex G-25, and Dowex 50 column and paper chromatography. Nine peptide fractions were purified to apparent homogeneity judging by thin-layer and ion-exchange column chromatography, and amino acid composition. Amino acid sequences of the peptides were determined: 2 were found to be mixtures of peptides and the sequence of another was only partially determined. Six of the peptides were potent inhibitors of the converting enzyme, while the other three were less active. 6 peptides were substrates for the enzyme. The enzyme released a dipeptide, Ala-Hyp from one peptide and was strongly inhibited by this dipeptide. The remainder of the parent peptides was a less effective inhibitor.     

The synthesis of evernitrose and 3-epi-evernitrose

Evernitrose (2,3,6-trideoxy-3-C-methyl-4-O-methyl-3-nitro-L-arabino-hexopyranose) was synthesized from methyl 2,6-dideoxy-4-O-methyl-α-L-erythro-hexopyranosid-3-ulose (2) through introduction of an amino group attached to the tertiary branching carbon by the method of Bourgeois, and subsequent oxidation of the amino group by m-chloroperoxybenzoic acid to a nitro group. 3-Cyano-3-O-mesylation of 2 by Bourgeois's method gave exclusively the desired product having the L-ribo configuration; furthermore, the β anomer of 2 gave the L-ribo and L-arabino products in the ratio of 1:2. The latter compound was converted into 3-epi-evernitrose by a similar sequence of reactions.     

Hydrophobic interactions of cytochrome c oxidase. Application to the purification of the enzyme from rat liver mitochondria.

The binding of rat liver cytochrome c oxidase to phenyl-Sepharose and various alkyl and omega-aminoalkyl agarose gels has been studied. Deoxycholate-solubilized cytochrome c oxidase was tightly bound to hexyl, octyl, omega-aminohexyl, omega-aminooctyl agarose as well as to phenyl-Sepharose. This hydrophobic interaction was used for the purification of cytochrome c oxidase. The enzyme which was eluted from phenyl-Sepharose was devoid of NADH (NADPH)-acceptor reductase activities. The heme a content was 15.4 nmol per mg of protein. The purified enzyme was resolved into seven polypeptides upon polyacrylamide gel electrophoresis in sodium dodecylsulfate with molecular weights of 40,000, 23,200, 21,500, 14,500, 12,600, 8900, and 4900. Antibodies raised in rabbits against the pure enzyme did not cross-react with cytochrome c oxidases from either beef heart or yeast mitochondria. Cytochrome c oxidase bound to octyl-Sepharose or phenyl-Sepharose exhibited a very low catalytic activity. The possible modes of interaction of cytochrome c oxidase with the hydrophobic ligands are discussed.     

Oxidative Degradation of Squalene by Arthrobacter Species

An organism isolated from soil and identified as Arthrobacter sp. was studied for its squalene degradation. The degradation product from squalene, which accumulated in the culture broth, was isolated and identified as trans-geranylacetone by mass spectrometry, gas chromatography, infrared spectrometry, and nuclear magnetic resonance spectrometry. Addition of a high concentration of K₂HPO₄ to the culture medium resulted in accumulation of fairly large amounts of carboxylic acids in addition to geranylacetone. These carboxylic acids were identified as isovaleric, β,β′-dimethylacrylic, geranic, and (+)-(R)-citronellic acids. Among these acids, α,β-saturated carboxylic acids were found to be predominant in quantity.     

Limited proteolysis of a chemically modified third component of human complement, C3, by cathepsin G of human leukocytes

We have investigated the limited proteolysis of the third component of complement, C3, by a human leukocyte protease, cathepsin G, by using a chemically modified C3, which was prepared by treatment of C3 with methylamine and a fluorescent thiol reagent, N-(dimethylamino-4-methylcoumarinyl)-maleimide (DACM) and was thus named DACM-C3me. Although native C3 was hardly cleaved by cathepsin G, DACM-C3me was cleaved by cathepsin G into three major fragments, which were termed C3c-G (150,000 daltons, 150 kd), C3d-G (25 kd), and C3a-G (10 kd). C3c-G was composed of four disulfide-linked polypeptide chains of 75 kd, 35 kd, and two 25 kd. C3d-G and C3a-G were single-chain fragments derived from the alpha chain. The N-terminal sequence of C3d-G was determined as Thr-Glu-Asp-Ala-Val-, suggesting that cathepsin G released C3d-G by cleaving a Met-Thr peptide bond which is located at 19 residues toward the N-terminal from the cysteinyl residue forming an internal thiolester linkage in native C3. C3d-G, like C3d-K (a C3d fragment produced by the action of plasma kallikrein), was found to have bioactivities such as leukocytosis-inducing and immunosuppressive activities.