Nonspecific reaction of a thiol: protein disulfide oxidoreductase with the disulfide bonds of insulin

A thiol: protein disulfide oxidoreductase from bovine liver was isolated after separation from protein disulfide isomerase. The enzyme, after activation (reduction) with glutathione, was reacted with stoichiometric amounts of insulin and the sulfhydryl groups of the partially reduced hormone were labeled with iodo (l-14C)acetamide. After separation of the insulin chains, the radioactivity was found in both the peptides, with a ratio A-chain/B-chain equal to 2/1.     

Biotransformation of the flavonoid tiliroside to 7-methylether tiliroside: bioactivity of this metabolite and of its acetylated derivative

Incubation of kaempferol-3-O-β-D-(6"-E-p-coumaroyl)-glucopyranoside (tiliroside) (1) with Aspergillus nidulans gives the 7-methyl ether of tiliroside (2) which is a new compound. Its structure is determined by spectroscopic methods. Cytotoxic studies of 2 and of its acetylated derivative 2a were carried out in vitro against fourteen human leukemic cell lines. Results clearly show that compound 2 is ineffective against all leukemic cell lines tested. On the contrary, compound 2a exhibited cytotoxic activity against four of the cell lines (HL60, DAUDI, HUT78 and MOLT3) and additionally, a dose- and time-dependent effect on DNA synthesis. Received 18 February 1997; received after revision 8 April 1997; accepted 6 May 1997     

Resistance of purified cholera toxin to enzymatic treatment with pancreatic elastase and papain

Summary Treatment of Cholera toxin with pancreatic elastase and papain in vitro shoed a high resistance of the toxin molecule to these enzymes, under non-denaturing conditions or in the presence of 2M urea. These experiments support the hypothesis of a particularly stable molecular structure of the toxin, as an explanation of its activity in the intestinal lumen where the pancreatic proteases are active.     

Biological activity of flucycloxuron,a novel benzoylphenylurea derivative,onTenebrio molitor: comparison with diflubenzuron and triflumuron

Flucycloxuron, a novel benzoylphenylurea (BPU) derivative, exhibited insecticidal activity when injected into newly ecdysed pupae ofTenebrio molitor. Mortality occurs because of defective adult ecdysis. Treatment caused a reduction in both cuticle thickness and incorporation of¹⁴C-labelled precursor into chitin, although it had no significant effect on the protein synthesis. The potencies of other BPU compounds as inhibitors of chitin biosynthesis have been examined and results showed that diflubenzuron was less effective than either flucycloxuron or triflumuron.     

Ascorbic acid and cholesterol: Effect of graded oral intakes on cholesterol conversion to bile acids in guinea-pigs

Summary A significant correlation between liver ascorbic acid (AA) and total bile acids or liver bile acids has been established in guinea-pigs by direct determination of the bile acids, confirming an earlier hypothesis. The oxidation of cholesterol to bile acids is dependent on the AA status, but it cannot be further stimulated by AA when the animals are already on an adequate intake of the vitamin. This suggests that AA has a hypocholesterolaemic effect over a limited range of AA status.     

Transannular reaction between ester and amide groups. Formation of a cyclol peptide derivative

Zusammenfassung Es wird die Synthese des Laktons (III) von Glykokoll-L-leucyl-L-prolin (IV) beschrieben. Spektroskopische Untersuchungen zeigen, dass das Lakton (III) eine durch Säure katalysierte transannulare Reaktion unter Bildung des Cyclol-Peptid-Derivats (II) durchläuft.     

Increase of free 5-hydroxytryptamine in blood plasma by reserpine and a benzoquinolizine derivative

Zusammenfassung Nach Vorbehandlung von Kaninchen mit einem Monoaminoxydase-Hemmer des Hydrazin-Typs wurde plättchenreiches Plasma mit Reserpin und einem Benzochinolizin-Derivat inkubiert. Im Plasma kam es dadurch zu einem Anstieg des nicht an Thrombozyten gebundenen 5HT, der dem Abfall des Amins in den Thrombozyten entsprach. Bei Kontrolltieren (ohne Monoaminoxydase-Hemmer) führte die Inkubation von plättchenreichem Plasma mit Reserpin zu keinem Anstieg des freien 5HT im Plasma, obgleich es in den Thrombozyten zu einer starken Senkung des Amins kam.

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Supported by a grant from the Finnish Medical SocietyDuodecim.     

Enzymatic reduction of fatty acids and acyl-CoAs to long chain aldehydes and alcohols

The properties of enzymatic systems involved in the synthesis of long chain aldehydes and alcohols have been reviewed. Fatty acid and acyl-CoA reductases are widely distributed and generate fatty alcohols for ether lipid and wax ester synthesis as well as fatty aldehydes for bacterial bioluminescence. Fatty alcohol is generally the major product of fatty acid reduction in crude or membrane systems, although reductases which release fatty aldehydes as products have also been purified. The reduction of fatty acid proceeds through the ATP-dependent formation of acyl intermediates such as acyl-CoA and acyl protein, followed by reduction to aldehyde and alcohol with NAD(P)H. In most cases, both the rate of fatty acid conversion and acyl chain specificity of the reaction are determined at the level of reduction of the intermediate. The reduction of fatty acids represents the major pathway for the control of the synthesis of fatty aldehydes and alcohols. Several other enzymatic reactions involved in lipid degradation also release fatty aldehydes but do not appear to play an important role in long chain alcohol synthesis.     

Enzymatic reduction of fatty acids and acyl-CoAs to long chain aldehydes and alcohols

Summary The properties of enzymatic systems involved in the synthesis of long chain aldehydes and alcohols have been reviewed. Fatty acid and acyl-CoA reductases are widely distributed and generate fatty alcohols for ether lipid and was ester synthesis as well as fatty aldehydes for bacterial bioluminescence. Fatty alcohol is generally the major product of fatty acid reduction in crude or membrane systems, although reductases which release fatty aldehydes as products have also been purified. The reduction of fatty acid proceeds through the ATP-dependent formation of acyl intermediates such as acyl-CoA and acyl protein, followed by reduction to aldehyde and alcohol with NAD(P)H. In most cases, both the rate of fatty acid conversion and acyl chain specificity of the reaction are determined at the level of reduction of the intermediate. The reduction of fatty acids represents the major pathway for the control of the synthesis of fatty aldehydes and alcohols. Several other enzymatic reactions involved in lipid degradation also release fatty aldehydes but do not apear to play an important role in long chain alcohol synthesis.     

Synthesis and metabolism of vertebrate-type steroids by tissues of insects: a critical evaluation

This review covers the synthesis and the metabolism of vertebrate-type steroids (progesterone, testosterone, estradiol, corticosteroids) by insect tissues and discusses the significance of the reactions for insect physiology. Biosynthesis of vertebrate-type steroids from cholesterol hitherto has been demonstrated in only two insect species, i.e. the water beetle Acilius sulcatus (Coleoptera) and the tobacco hornworm Manduca sexta (Lepidoptera). In Acilius, steroid synthesis is associated with exosecretion (chemical defense). Nothing, however, is known about a physiological role of the C21 steroid conjugate present in ovaries and eggs of Manduca. No synthesis of vertebrate-type steroids was observed in any other insect investigated to date. Most metabolic conversions of steroids by insects concerned oxidoreduction of oxygen groups (hydroxysteroid dehydrogenase activity) and (polar and apolar) conjugate formation. All important enzymatic steps involved in synthesis and catabolism, as known from studies with tissues of vertebrates, were not, or hardly observed. The conclusion is drawn that typical vertebrate-type (C21, C19 and C18) steroids probably do not act as physiologically active substances in insects.     

Detection and identification of pyridosine,a second lysine derivative obtained upon acid hydrolysis of heated milk

Résumé Un deuxième dérivé de la lysine inactivée, l'-(1, 4-dihydro-6-methyl-3-hydroxy-4-oxo-1-pyridyl)-L-lysine, a été trouvé dans les hydrolysats de laits surchauffés; il se forme à partir de la deoxy-D-lactulose-L-lysine et peut être mis en évidence dans des conditions particulières de chromatographie. Sa structure a été déterminée par spectrométrie de masse, UV, IR et RMN; le nom de pyridosine est proposé pour ce nouvel acide aminé.