An active site-tyrosine-containing heptapeptide from D-amino acid oxidase

The flavoenzyme D-amino acid oxidase (Eo) is rapidly chlorinated by N-chloro-D-leucine (Rudie, N.G., Porter, D.J.T., and Bright, H.J. (1980) J. Biol. Chem. 255, 498-508). We have carried out chymotryptic digestion of E0-36Cl2 and find that all of the radiolabel is located in a heptapeptide having [3.5-36Cl2]chlorotyrosine as the COOH-terminal residue. This heptapeptide, having the sequence -Asp-Leu-Glu-Arg-Gly-Ile-Tyr-, is located within a larger fragment obtained previously from cyanogen bromide cleavage of E0. These results demonstrate that the target for chlorination in E0 must be a single tyrosine residue and provide, when taken together with previous findings, the first clear evidence for the identity and location of an active site residue in the polypeptide chain of D-amino oxidase.     

Effect of low ambient temperature on protein turnover and heat production in chicks

1. Effect of low ambient temperature on protein turnover in the liver and whole body was investigated in chicks together with the contribution of protein synthesis to the total heat production. 2. Both protein synthesis and degradation in the whole body were increased, the latter to a larger extent, at low ambient temperature (LT, 22 degrees C) compared with adequate temperature (AT, 30 degrees C). Liver protein synthesis was not significantly altered by the temperature treatment. 3. The total heat production of LT group was as high as 160% of the AT group. 4. The increased heat production due to enhanced whole-body protein synthesis accounted for only 1.4% of the heat increment in thermogenesis at low ambient temperature, suggesting that protein synthesis would contribute little, if any, to cold-induced thermogenesis in chicks.     

Concerning the structure of photobilirubin II.

Evidence is presented which supports the postulate that the photobilirubins IIA and IIB are diastereoisomers in which the C-3 vinyl group has cyclized intramolecularly. The evidence comes principally from proton n.m.r. spectroscopy at 400 MHz and from chemical considerations. The cyclic structures require the E-configuration at the C-4 double bond in the precursor; this is the first structural evidence for the Z leads to E isomerization in bilirubin and supports the view that the precursor (photobilirubin IA or IB) is (4E, 15Z)-bilirubin. Brief irradiation of photobilirubin II gives bilirubin, a new compound (photobilirubin III) and unchanged starting material. The various photoisomers are discussed in terms of their inter-relationships and biological fates.     

Chemical taxonomy of the hinge-ligament proteins of bivalves according to their amino acid compositions.

The proteins in the hinge ligaments of molluscan bivalves were subjected to chemotaxonomic studies according to their amino acid compositions. The hinge-ligament protein is a new class of structure proteins, and this is the first attempt to introduce chemical taxonomy into the systematics of bivalves. The hinge-ligament proteins from morphologically close species, namely mactra (superfamily Mactracea) or scallop (family Pectinidae) species, showed high intraspecific homology in their compositions. On the other hand, inconsistent results were obtained with two types of ligament proteins in pearl oyster species (genus Pinctada). The results of our chemotaxonomic analyses were sometimes in good agreement with the morphological classifications and sometimes inconsistent, implying a complicated phylogenetic relationship among the species.     

Specificity of the collagenolytic enzyme from the fungus Entomophthora coronata: comparison with the bacterial collagenase from Achromobacter iophagus.

The specificity of the collagenolytic enzyme from the fungus Entomophthora coronata toward some inhibitors and the B chain of oxidized insulin was investigated and compared to that of the bacterial collagenase from Achromobacter iophagus. The fungal enzyme was completely inhibited by diisopropylfluorophosphate, tosyl-l-lysine chloromethyl ketone, and tosyl-amino-2-phenylethyl chloromethyl ketone but not at all by ethylenediaminetetraacetate. This indicates that it is not a metalloenzyme like the bacterial Achromobacter collagenase. The B chain of insulin was not hydrolysed at all by the bacterial enzyme under conditions where extensive digestion was observed with the Entomophthora enzyme. The fungal enzyme cleaves preferentially the bonds $\text{Leu}\text{15}\text{-}\text{Tyr}\text{16}\text{and}\text{Leu}\text{11}\text{Val}\text{12}$ as determined by automatic sequencing; the secondary cleavages were identified by a systematic analysis of the digestion mixture; thus, the fungal collagenolytic enzyme from Entomophthora coronata differs both structurally and functionally from the bacterial Achromobacter collagenase.     

The mechanism of the hypolipidemic effect of garlic oil extract in rats fed on high sucrose and alcohol diets

The effect of feeding garlic oil to white albino rats maintained on high sucrose and alcohol diets was studied. It is proposed that the mechanism of the hypolipidemic effect of the oil involves the active principle, diallyl disulphide, inactivating enzymes and substrates containing thiol groups in an exchange reaction; increased hydrolysis of triacylglycerols as increased lipase activity is induced by the oil; and the reduction in the biosynthesis of triacylglycerols as NADPH is made unavailable for the process by the metabolism of the oil.     

Human skin chymotrypsin-like proteinase chymase. Subcellular localization to mast cell granules and interaction with heparin and other glycosaminoglycans

The subcellular localization of human skin chymase to mast cell granules was established by immunoelectron microscopy, and binding of chymase to the area of the dermo-epidermal junction, a basement membrane, was demonstrated immunocytochemically in cryosections incubated with purified proteinase prior to immunolabeling. Because heparin and heparan sulfate proteoglycans are major constituents of mast cell granules and basement membranes, respectively, the ability of chymase to bind to glycosaminoglycans (GAG) was investigated. Among a variety of GAGs, only binding of chymase to heparin and heparan sulfate appears physiologically significant. Binding was ionic strength-dependent, involved amino groups on the proteinase, and correlated with increasing GAG sulfate content, indicating a predominantly electrostatic association. Interaction with heparin was observed in solutions containing up to 0.5 M NaCl, and interaction with heparan sulfate was observed in solutions containing up to 0.3 M NaCl. Binding of heparin did not detectably affect catalysis of peptide substrates, but may reduce accessibility of proteinase to protein substrates. Measurements among a series of serine class proteinases indicated that heparin binding was a more common property of mast cell proteinases than proteinases stored in other secretory granules. Binding of chymase to heparin is likely to have a storage as well as a structural role within the mast cell granule, whereas binding of chymase to heparan sulfate may have physiological significance after degranulation.