The synthesis of acetyl phosphate by homogenates of elasmobranch liver

• 1.1. Cetyltrimethylammonium bromide extracts of elasmobranch liver are shown to have acetyl kinase activity. The conditions resulting in activity are different from those resulting in carbamoyl phosphate synthetase activity in the same tissue. The possibility that the two activities are due to the same enzyme, however, is not ruled out.
• 2.2. Progress curves suggesting that a time-dependent activation process may be involved in the case of aged and frozen extracts were obtained.
• 3.3. Omission of N-acetyl glutamate from the assay mixture reduces acetyl kinase activity by about 30 per cent.

     

Monoclonal antibodies neutralizing the haemolytic activity of box jellyfish (Chironex fleckeri) tentacle extracts

• 1.1. Three monoclonal antibodies have been produced which neutralize in vitro the haemolytic activity present in tentacle extracts of the box jellyfish (Chironex fleckeri).
• 2.2. Two of these monoclonal antibodies bound specifically to a component of relative molecular mass 50,000 in tentacle extract on Western blots.
• 3.3. This binding only occurred when the extracts were electrophoresed under non-reducing conditions.
• 4.4. The third monoclonal antibody did not display binding to Western blots of tentacle extract under any of our experimental conditions.

     

Ribosome inactivating protein-like activity in seeds of diverse Cucurbitaceae plants

• 1.1. Seed extracts of 20 plants species belonging to the family Cucurbitaceae were examined for their ability to inhibit protein synthesis in rabbit reticulocyte lysate and induce mid-term abortion in mice.
• 2.2. Eleven extracts were found to inhibit protein synthesis by about or over 90%, seven extracts produced about 80% inhibition, one caused about 70% inhibition and one brought about approx. 40% inhibition, when the extracts were tested at a final concentration of 10 μg per ml.
• 3.3. All of the seed extracts possessed potent mid-term abortifacient activity.
• 4.4. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the seed extracts disclosed the existence of a Coomassie Blue-stainable band with a mol. wt of ca 30,000 Da. This band probably accounts for the protein synthesis inhibiting and mid-term abortifacient activities.
• 5.5. There was a similarity in the electrophoretograms of seed extracts of plants belonging to the same genus.

     

Dipeptidyl aminopeptidase activities of guinea-pig brain

• 1.1. The subcellular distribution ofdipeptidyl aminopeptidase activities in guinea-pig brain was investigated. Our studies show that DAP I (Gly-Arg-NH-Mec hydrolase) type activity was found to have an acidic optimum and was associated with the nuclear pellet.
• 2.2. No DAP II (Lys-Ala-NH-Mec hydrolase) type activity could be detected. Apparant hydrolysis was mainly due to aminopeptidase activity.
• 3.3. DAP III (Arg-Arg-NH-Mec hydrolase) type activity is largely cytoplasmic, but there was evidence of a membrane form associated with the synaptosomes.
• 4.4. DAP IV (Gly-Pro-NH-Mec hydrolase) type activity is present on the synaptosomal membrane, and also enriched in the microsomes. A soluble form of Gly-Pro-NH-Mec hydrolase activity is also present in the cytoplasm. Whether this activity is a DAP II or IV type activity is still yet to be determined.

     

Digestion of protein in different marine species

• 1.1. The digestion proteases in five marine species (Atlantic halibut, Hippoglossus hippoglossus (L); Dover sole, Solea solea (L); turbot, Scophthalmus maximus, (L); European lobster, Hommarus gammaarus (L); and the giant prawn, Penaeus monodon) have been compared by biochemical methods.
• 2.2. The pH profiles for the hydrolysis of casein by extracts from the digestive systems of each species showed different characteristics; extracts from adult halibut, turbot and sole exhibited strong pepsin-like activity; whereas this enzyme was absent in P. monodon and in sole larvae.
• 3.3. Although lobster extracts, from either the hepatopancreas or the stomach, showed peaks at pH values of 5.8 and 2.5, this latter activity did not hydrolyse a specific substrate for pepsin.
• 4.4. Halibut and turbot digestive extracts contained an activity optimal at pH values in the region of 5.0 resembling a cathepsin-like enzyme; an activity which was not evident in the other species under similar experimental conditions.
• 5.5. Although all species possessed trypsin-like activity, the pH profiles of activity in the neutral to alkaline region were unique to each species.
• 6.6. The significance of these results is considered with respect to the anatomical differences in the alimentary systems of these species.

     

Investigation of ribosome inactivating protein-like activity in tissues of cucurbitaceae plants

• 1.1. Extracts of roots, seeds and fruits of seventeen plant species belonging to Family Cucurbitaceae were examined for the ability to inhibit protein synthesis in rabbit reticulocyte lysate and induce mid-term abortion in mice.
• 2.2. Out of the 22 tissue extracts examined, 16 were found to inhibit protein synthesis by >90%, three caused 65–85% inhibition and 3 caused <25% inhibition.
• 3.3. In general, there was a close correlation between protein synthesis inhibiting activity and mid-term abortifacient activity of the tissue extracts.
• 4.4. SDS-PAGE of the tissue extracts revealed the presence of a Coomassie Blue-stainable band with a mol. wt of ca 30,000. The data suggest that this band is responsible for the protein synthesis inhibiting and mid-term abortifacient activities.

     

Purification and some properties of an atypical alkaline p-nitrophenylphosphate phosphatase activity from Halobacterium halobium

• 1.1. An alkaline p-nitrophenylphosphate phosphatase has been purified 440-fold from extracts of Hatobacterium halobium.
• 2.2. The enzyme has an apparent molecular weight of 24,000.
• 3.3. A K_m value for p-nitrophenylphosphate of 1.12mM has been found under optimal conditions.
• 4.4. The enzyme is selectively activated and stabilized by Mn²⁺.
• 5.5. It requires high salt concentrations for stability and maximum activity.
• 6.6. It displays an unusual restricted substrate specificity of 25 phosphate esters tested, only phosphotyrosine and casein were hydrolysed besides p-nitrophenylphosphate.

     

Isolation of allantoin and adenosine from the marine sponge Tethya aurantia

• 1.1. Propanol extracts of the sponge Tethya aurantia (Demospongiae) were fractionated, guided by bioassay, for a component with negative chronotropic and inotropic activity on isolated guinea pig atria.
• 2.2. The bioactive component was found to be adenosine. These extracts also contained allantoin.
• 3.3. This intermediate in the sequence of degradation of purines was unexpected, since it has been reported only once before to occur in marine invertebrate animals.

     

Arginase activity in different fish species and tissues

• 1.1. Arginase activity was measured in different tissues from eight species of fish.
• 2.2. Spur dogfish showed a very high arginase activity compared with the other species analysed.
• 3.3. The activity in teleosts was mainly found in tissues of high metabolic activity (liver, kidney and red muscle).

     

Glycogen phosphorylase in lobster hepatopancreas: action of proteases on the enzyme

• 1.1. In lobster hepatopancreas, extracellular protreases cause the inactivation of glycogen phosphorylase.
• 2.2. The proteolysis of glycogen phosphorylase purified from rabbit muscle by these proteases has been shown by SDS-polyacrylamide gel electrophoresis.
• 3.3. A cell isolation technique has allowed us to remove proteases of extracellular digestion and to measure glycogen phosphorylase activity in lobster hepatopancreas.
• 4.4. The glycogen phosphorylase activity seems to be mainly associated with R cells while it could not be detected in B cells.

     

In vitro non-enzymatic glycosylation of myofibrillar proteins

• 1.1. Glycation is non-enzymatic modification of proteins by sugars in which not only structural but also biological properties of proteins are altered.
• 2.2. Our in vitro experiments show that incubation of myofibrillar proteins with ribose results in sugar attachment to proteins and at the same time myofibrillar ATPase activity is lowered.
• 3.3. DETAPAC, aminoguanidine and 2-mercaptoethanol all partially block myofibrillar protein glycation and ATPase activity is less inactivated.
• 4.4. The dependence of ATPase activity of myofibrils incubated with ribose on the amount of 2-mercaptoethanol present suggests that also modification of SH groups is involved in enzyme inactivation.
• 5.5. Electrophoretic studies revealed that heavy chains of myosin, actin, and tropomyosins are proteins which are mainly glycated in vitro.

     

Insulin administration induces capillary growth in brown adipose tissue of heat-exposed rats

• 1.1. An apparent effect of insulin administration on enlargement of interscapular brown adipose tissue (BAT) was found in heat-exposed rats, but not in warm-adapted or cold-acclimated rats.
• 2.2. BAT extracts from the heat-acclimated/insulin-treated (HI) rats notably increased the capillary growth in an in vitro angiogenesis model in which microvascular fragments and myofibroblastic (Mf) cells isolated from lipid tissues were grown in co-culture, although a direct effect of insulin was not high.
• 3.3. BAT extracts from the HI rats stimulated the production of endothelial cell growth factor and collagen by Mf cells.
• 4.4. It is probable that an increased angiogenic activity contributes to the capillary growth and tissue growth in BAT of HI rats.

     

Metabolic and contractile differentiation of rabbit muscles during growth

• 1.1. A study was carried out of post-natal evolution of the oxidative, glycolytic and contractile capacities in various types of rabbit muscle.
• 2.2. At birth, muscles are non-differentiated and present very limited metabolic and contractile activity, metabolism is mainly oxidative in all muscles.
• 3.3. Although muscular discrimination is manifest from the sixth week after birth, the glycolytic metabolism reaches its maximum capacity only after six to eight weeks.
• 4.4. Subsequently, oxidative metabolic capacity steadily decreases until adulthood.

     

Supply of polyenoic fatty acids to the mammalian brain: The ease of conversion of the short-chain essential fatty acids to their longer chain polyunsaturated metabolites in liver,brain, placenta and blood

The metabolism of linoleic and linolenic acids to the longer polyunsaturated fatty acids of mammalian brain is discussed. Differences in metabolic activity are considered between tissues, between species, and during different stages of development. Available evidence suggests that:

• 1.1. The sites of metabolism are confined mainly to liver and the brain itself.
• 2.2. The similar metabolic pathways are subject to a complex control which is most effective at the first step in the sequence.
• 3.3. During early development there are reciprocal changes in the metabolic capacity of brain and liver.
• 4.4. Metabolic activity varies between species and may be absent in obligate carnivores.

     

Effect of inorganic phosphate on synthesis of 5-phosphoribosyl-1-pyrophosphate in cultured plant cells

• 1.1. Inorganic phosphate (Pi) was absorbed rapidly by suspension-cultured cells of Catharanthus roseus which had previously been cultured in Pi-free Murashige Skoog medium.
• 2.2. The intracellular levels of ATP, ADP and 5-phosphoribosyl-l-pyrophosphate (PRPP) increased markedly during the 24 hr which followed the addition of Pi (1.25mM).
• 3.3. Availability of PRPP in vivo, estimated by the measurement of nucleotide synthesis from [8-¹⁴C]adenine, was also increased by addition of Pi.
• 4.4. Only a 20% increase in the maximum catalytic activity of PRPP synthetase was observed in extracts of cells, prepared 24 hr after addition of Pi.
• 5.5. In contrast to results for mammalian PRPP synthetase, the activity of PRPP synthetase, partially purified from Catharanthus roseus, was inhibited by concentration of Pi greater than 5mM.
• 6.6. The mechanisms involved in the increased availability of PRPP and the synthesis of adenine nucleotides in the plant cells cultured in Pi-containing medium are discussed.

     

Proteolytic system in Babesia hylomysci

• 1.1. Babesia hylomysci has an aminopeptidase and an acid endoprotease
• 2.2. The amino-peptidase has properties very similar to the aminopeptidase in Plasmodium yoelii nigeriensis and P. chabaudi.
• 3.3. The acid endoprotease is specific towards haemoglobin and practically has no action on bovine serum albumin.
• 4.4. In mouse normal red blood cells we find an acid protease having physico-chemical properties similar to the enzyme present in B. hylomysci extracts.
• 5.5. The similarity of electrophoretic velocity between acid protease in B. hylomysci and non-infected red blood cells leads us to think that the acid protease of parasitic extracts comes from the host-cell.
• 6.6. The proteolytic system of Babesia and Plasmodium are similar.

     

Activity of some enzymes involved in the metabolism of polyamines in the liver of streptozotocin-diabetic rats

• 1.1. The effect of diabetes on some enzymes of polyamine metabolism was studied in male rats 1–12 days after administration of streptozotocin.
• 2.2. Hepatic ornithine decarboxylase activity decreased in the first days after the administration, but increased thereafter. The decrease was not due to an alteration of the ODC-antizyme concentration, nor to a posttranslational modification catalyzed by transglutaminase.
• 3.3. S-adenosylmethionine decarboxylase and ornithine transaminase were both increased.
• 4.4. Spermicline acetyltransferase activity was practically unchanged, while its inactivating factor was markedly decreased.

     

δ-Aminolevulinic acid dehydratase inactivation by uroporphyrin I in light and darkness

• 1.1. The action of uroporphyrin I on erythrocytic ALA-D activity under dark and light conditions was examined.
• 2.2. Photo and non-photoinactivation of ALA-D induced by uroporphyrin I were observed.
• 3.3. Both effects were dependent on uroporphyrin concentration, temperature and time of exposure of the protein to the porphyrin.
• 4.4. Light-dependent effect of uroporphyrin I is related with the phototoxicity of porphyrins and could be produced by primary amino acid photooxidation followed by secondary cross-linking of the protein.
• 5.5. Light-dependent effect of uroporphyrin I could be ascribed to a direct enzyme inhibition due to binding of the porphyrin to the protein inducing structural changes at or near its active site.

     

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