[Stimulating effect of human chorionic gonadotropin on the activity of guanidinoacetate-N-methyltransferase of rat testes: role of cyclic AMP]. / Stimuliruiushchee vliianie khorional'nogo gonadotropina cheloveka na aktivnost' guanidinatsetat-N-metiltransferazy semennikov krys: Rol' tsiklicheskogo AMF

A study was made of the influence of human chorionic gonadotropin (HCGT) on the activity of guanidineacetate-N-methyltranspherase in human testes. Guanidineacetate-methyltranspherase proved to be stimulated in the testes of the sexually immature rats in vivo under the action of HCGT on the 19th day after birth and from the 24th to the 27th day after birth. The activity of the enzyme was also increased in adult rats weighing 35--40 g. The activity of guanidineacetate-methyltranspherase in the testes of rats was particularly sharply stimulated after a single administration of N6-O2'-dibutiryladenosine-3',5'-cyclophosphate against the background of a preliminary treatment of rats with HCGT for a period of 5 days. The enzyme stimulation induced by combined treatment of rats with HCGT and N6-O2'-dibutiryladenosine-3',5'-cyclophosphate was prevented by the administration of cycloheximide and actinomycine D. The activity of the enzyme decreased after the incubation of the rat testes tissue homogenate with HCGT.

[Regulation of L-asparaginase biosynthesis in mutants of Bacillus mesentericus 43A, poorly growing in the presence of aspartic acid]. / Reguliatsiia obrazovaniia L-asparaginazy u mutantov Bacillus mesentericus 43A, slabo rastushchikh v prisutstvii asparaginovoi kisloty

Biosynthesis of L-asparaginase (EC 3.5.1.1) was inhibited in the growing culture of Bac. mesentericus 43A on addition of L-aspartic acid (20 mM). My treatment with methyl nitrosourea (2 mg/ml) mutants were obtained, which grew poorly on aspartic acid used as the only source of carbon and nitrogen. The aspartic acid did not repress the asparaginase biosynthesis in 8 strains, found between the mutants. In six of these mutants the asparaginase biosynthesis was inhibited by means of the type of catabolite repression. The data obtained suggest that in Bac. mesentericus 43A the asparaginase biosynthesis is controlled more likely by two independent mechanisms: 1) specific repression with aspartic acid as an end product and 2) catabolite repression.

[Study of the structure of the histidine decarboxylase of Micrococcus sp. n. by the method of circular dichroism]. / Izuchenie struktury gistidindekarboksilazy Micrococcus sp. n. metodom kruglovogo dikhroizma

Ring dichroism spectra (RD) of histidine decarboxylase (HDC) from Micrococcus sp. n. at the regions of peptide bonds (200-240 nm) and aromatic amino acids (250-300 nm) absorption are studied. The treatment of RD spectra according to methods of Greenfield-Fasman, Saksena-Vetlaufer and Mayer permits to conclude that at the pH range within 4-8 the content of ordered structures of alpha-helix type comprises 20%, that of beta-structure type-40%, while the rest 40% are represented with polypeptide chain in a disordered globular state. When pH is varied from 1 to 12, the content of alpha-helices decreases from 17 to 5%. There are two distinct dichroic bands in the spectrum of aromatic chromophores absorption (at 270 and 290 nm), the former containing tirosine, tryptophane and phenylalanine residues and the latter being induced with triptophane residues. The study of HDC RD spectra at the regions of peptide bonds and aromatic acids absorption at different temperatures has shown that a part of triptophane, tyrosine and phenylalanine residues is in an ordered structure of the alpha-helix type. The HDC undergoes irreversible changes under heating to 70 degrees and in 8 M urea. 5 M guanidine chloride eliminates the ordered HDC structure, while sodium dodecylsulphate at concentrations up to 1% does not affect the enzyme structure.

[The stimulating effect of cyclic AMP, glucagon and insulin on guanidine acetate-N-methyltransferase activity in rat liver and pancreas]. / Stimuliruiushchee vliianie tsiklicheskogo AMP, gliukagona i insulina na aktivnost' guanidinatsetat-N-metiltransferazy v pecheni i podzheludochnoi zheleze krys

N6,O2'-dibutyrylcyclo-3',5'-AMP injected to intact rats alone or in combination with theophylline increases the activity of guanidine acetate methyltransferase (GAMT) in liver and pancreas. Cyclic 3',5'-AMP and its dibutyryl analog administered immediately or two hours after the suturing of common bile duct (SCBD) stimulate the increase of pancreatic GAMT activity 2-3 fold. Glucagon, injected intraabdominally simultaneously with SCBD and administration of theophylline, dramatically increases the theophylline effect on the GAMT activity. The freezing of rat pancreas pretreated witn secretin, a hormone structurally similar to glucagon, results in a 1.5-2-fold increase of creatine synthesis from S-adenosylmethionine and guanidinacetic acid. An hour after glucagon administration to intact rats the GAMT activity of liver increases 9 times. The effect of glucagon is enhanced by insulin. Cycloheximide inhibits the increase of GAMT activity, induced by glucagon or a combination of glucagon and insulin. Experiments on tissue homogenates demonstrate that 3',5'-AMP in concentrations of 10(-8) --10(-2) M does not affect the GAMT activity or to some extent inhibits the enzyme. The homogenate incubation in a medium containing 10(-5) M epinephrine or 10(-7) M caffeine and 5 mM Mg2+ leads to an increase in the GAMT activity. Oligomycin removes the stimulating effects of caffeine and Mg2+ on the enzyme activation. This is probably due to the presence of 3',5'-AMP-dependent protein kinase in the mechanism of GAMT activation by cyclic AMP.

[Isolation, purification and properties of a carboxypeptidase inhibitor from human blood serum]. / Vydelenie, ochistka i svoistva ingibitora karboksipeptidazy i iz syvorotki krovi cheloveka

Partially purified low molecular component, which inhibited the carboxypeptidase N activity in samples with hippuryl-L-lysine and bradikinine as substrates, was isolated from human blood serum by means of chromatography on DEAE-Sephadex, ultrafiltration of the fractions obtained through Amicon membranes UM-10 or UM-2 and subsequent gel filtration through Sephadex G-10. The probable molecular weight of the inhibitor was 2000. The inhibitor was thermolabile; its inhibitory activity was decreased by 50% after 30 min boiling in 0.01 M phosphate buffer, pH 7.8. Trypsin and chymotrypsin did not influence the inhibitory properties of the factor. Hydrolysis of the low molecular component in 6 N HCl at 110 degrees C within 18 hrs and subsequent studies of the amino acid composition showed a number of amino acids in the hydrolysate; the hydrolysate exhibited the inhibitor activity of the initial substance.

[Purification of deamidase AG (asparaginase-glutaminase) from Pseudomonas fluorescens AG and some physicochemical properties of the enzyme]. / Ochistka dezamidazy AG (asparaginazy-gliutaminazy) iz Pseudomonas fluorescens AG i nekotorye fiziko-khimicheskie svoistva fermenta

Deamidase AG (asparaginase-glutaminase) was obtained from Pseudomonas fluorescens in a crystalline apparently homogenous state. Molecular weight of the enzyme, determined by acrylamide gel electrophoresis, was equal to 128 000 daltons; by ultracentrifugation (56100 rev/min, 65 min, 20.5 degrees C) coefficient of sedimentation was shown to be 7.36 S. Optimal pH for asparaginase activity of the enzyme was at pH 8.0-9.0, for glutaminase activity--at pH 5.5-7.5.

[Purification of microbial asparaginases by the aid of affinity chromatography]. / Ochistka mikrobnykh asparaginaz s pomoshch'iu khromatografii po srodstvu

Asparaginases from Escherichia coli and Erwinia caratovora were isolated and purified by column chromatography with a specific sorbent (sepharose, covalently bound to N-alpha-(6-aminohexyl)-D-asparagine). Homogenous asparaginase from E. coli was isolated by one-step procedure, while the enzyme from Er. carotovara was 50-60-fold purified. Asparaginase from Mycobacterium n. sp. was found not to bind with the specific sorbent.