[Hormonal activity of the ACTH(4-10) analog--a prolonged-action stimulant of learning]. / Gormonal'naia aktivnost' analoga AKTG4-10--stimuliatora obucheniia prologirovannogo deistviia.

Possible hormonal activity of ACTH4-7, a long-acting ACTH4-10 analog (ProGly Pro) was studied. Unlike ACTH5-10 the peptide did not reveal steroidogenic and melanocyte-stimulating activity.

[Synthesis of [cyclo(Glu gamma-----epsilon Lys(Gly)]ACTH-(5-14) undecapeptide. Biological and physico-chemical properties of analogs of ACTH-(5-10)- and ACTH-(5-14)-peptides]. / Sintez [tsiklo(Glu gamma----epsilon Lys(Gly)]-ACTH-(5-14) undekapeptida. Biologicheskie i fiziko-khimicheskie svoistva analogov ACTH-(5-10)- i ACTH-(5-14)-peptidov.

Modified corticotropin fragment - [Lys11 (Gly)]ACTH-(5-14)- and its cyclic analogue - [cyclo (Glu gamma----epsilon Lys (Gly)] ACTH-(5-14)-undecapeptides have been synthesized by classical approach. The cyclic structure has been fixed by amide bond between gamma-COOH group of glutamic acid and alpha-NH2 group of glycine coupled to the epsilon-NH2 group of lysine. Fragment condensation has been achieved by azide or dicyclohexylcarbodiimide methods. Cyclization has been performed using diphenylphosphorylazide. The melanotropic activity of the cyclicanalogue on isolated frog skin exceeds by two orders of magnitude that of the linear undecapeptide, however the steroidogenic activity in isolated cells of rat adrenal cortex is diminished by an order of magnitude as compared with that of the linear precursor. A similarity of the CD spectra for the cyclic ACTH peptides and their linear counterparts in water and trifluoroethanol points to the similarity and relative rigidity of their structures.

[Synthesis and biological properties of a cyclic analog of ACTH-(5-14)-decapeptide]. / Sintez i biologicheskie svoistva tsiklicheskogo analoga ACTH-(5-14)-dekapeptida.

A cyclic analogue and the corresponding linear segment of the corticotropin molecule, namely ACTH-(5-14)- and [cyclo (Glu gamma-epsilon Lys)]ACTH-(5-14)-decapeptide, both including the specific and unspecific active centers of the ACTH molecule, have been synthesized and studied. The cyclic structure is fixed by amide bond between the glutamic acid and lysine side chains. Condensation of fragments has been realized by azide or DCC/HOBT methods. Cyclization has been achieved using diphenylphosphorylazide. The cyclic analogue has full steroidogenic activity, while its melanotropic activity is 3 orders of magnitude higher than that of the linear decapeptide.

[Synthesis and analysis of potent cyclic analogs of the ACTH active center]. / Sintez i issledovanie vysokoaktivnykh tsiklicheskikh analogov aktivnogo tsentra kortikotropina.

Linear and cyclic analogues of the specific active center of the ACTH molecule have been synthesized, viz. [Lis5]ACTH-(5-10)-, [Lys5, cyclo (Gly10----epsilon Lys5)]-ACTH-(5-10)-hexapeptides, [Lys5 (Gly)]ACTH-(5-10)- and [Lys5, Gly11, cyclo (Gly11----epsilon Lys5)]-ACTH-(5-11)-heptapeptides. The cyclic structures are fixed by covalent bond between the COOH-group of the C-terminal glycine and epsilon-amino group of a lysine residue. Azide method, DCC/HOBT or pentafluorophenyl esters are used for fragment coupling, while cyclization is achieved by means of diphenylphosphoryl azide or pentafluorophenyl esters. Cyclic compounds are 2-3 orders of magnitude more active than their linear counterparts as revealed by assaying their melanocyte-stimulating activity in vitro on frog skin. Only the title heptapeptide possesses a steroidogenic activity similar to that of ACTH-(5-10)-hexapeptide. The results obtained are in accord with the idea implying the formation in the hormone-receptor complexes of quasi-cyclic structures in the region of the specific active center of ACTH molecule.

[Structural and functional organization of ACTH: synthesis and properties of analogs of ACTH-(11-24)-tetradeca- and ACTH-(1-24)-tetracosapeptides containing hexa-amino acids instead of a natural sequence of ACTH 19-24 amino acids]. / Strukturno-funktsional'naia organizatsiia ACTH: sintez i svoistva analogov ACTH-(11-24)-tetradeka- i ACTH-(1-24)-tetrakozopeptidov, soderzhashchikh geksaaminokisloty vmesto prirodnoi posledovatel'nosti aminokislot ACTH 19-24.

To assess the role of amino acid sequence ACTH 19-24 in the corticotropin structure and steroidogenic activity, the analogues of ACTH-(11-24)-tetradeca- and ACTH-(1-24)-tetracosapeptides containing hexaglycine, hexaphenylalanine, hexaglutamic acid or hexalysine instead of the natural 19-24 sequence have been synthesized by conventional methods. All these compounds in water have the CD curves characteristic of random coil, CD spectra of analogue ACTH-(1-24)-tetracosapeptide and hexalysine-containing analogue ACTH-(11-24)-tetradecapeptide in trifluoroethanol indicate the presence of alpha-helices. The latter compound manifested higher steroidogenic activity than ACTH-(11-24)-tetradecapeptide. All the other analogues were either less active than ACTH-(1-24)-tetracosapeptide or inactive over the concentration range 10(-5)-10(2) mg/ml, thereby testifying to functional importance of the 19-24 sequence for manifesting full steroidogenic activity.

[Structure-function organization of ACTH: fragment ACTH 11-24--a functionally important site of the hormone molecule]. / Strukturno-funktsional'naia organizatsiia AKTG: fragment AKTG 11-24--funktsional'no vazhnyi uchastok molekuly gormona.

The steroidogenic and lipolytic activities of ACTH fragments (ACTH11-24--I, ACTH11-19--II, ACTH11-16--III and ACTH 17-24--IV) were studied. Fragments I--IV exert a steroidogenic effect in isolated fasciculata rat adrenal cells at concentrations of 1--500 micrograms/ml. The inner activity (alpha) and concentration at which a half-maximum effect is achieved (EC50) for fragments I and IV are 0.64+/-0.09 and 0.5--2.0 micrograms/ml, for fragment III--0.49+/-0.07 and 0.7 microgram/ml, respectively. Fragments I--IV have no effect on the lipolysis in isolated rat fat cells. The results obtained are indicative of the functional importance of fragment ACTH11-24 in manifestation of steroidogenic action of ACTH and suggest that the second active site of ACTH is enclosed within this amino acid sequence.

[Comparison of structural and functional organization of adrenocorticotropic hormone and wasp kinin]. / Sravnenie strukturno-funktsional'noi organizatsii molekuly aktg i kinina iz iada osy

A comparative study of structural and functional organization of the polypeptides -- ACTH and wasp kinin was made. The effects of fragments Lys 17, 18-ACTH11(-18)-NH2--(I) and WK4(-12)--(II), possessing "common" fragments and a cluster of basic amino-acids, on the lipolytic and steroidogenic effects of ACTH and myotropic effects of bradykinin were studied. Both fragments I and II potentiate ACTH-induced lipolysis and steroidogenesis in isolated rat fat and adrenal cells but suppress the myotropic effect of bradykinin on guinea pig ileum. The similarity of biological effects of ACTH and WK fragments support our supposition on the similarity in structurally functional organization of these peptides.

[Structurally functional organization of corticotropin: lipolytic and steroidogenic activity of some of its fragments]. / Strukturno-funktsional'naia organizatsiia aktg: lipoliticheskaia i steroidogennaia aktivnost' nekotorykh fragmentov molekuly

The influence of ACTH fragments, possessing structural elements, common for certain groups of peptide hormones and kinins--"common" fragments and cluster of basic amino-acids--(Lys 17,18-ACTH 11-18-NH2--I; ACTH 11-13-NH2--II; NH2CO-ACTH18-20-NH2--III) on lipolytic effect of ACTH in rat isolated fat cells and on the steroidogenic effect of ACTH in isolated rat adrenal cells was studied. Fragment I exerts a steroidogenic effect (alpha=0,84) at concentrations of 1--100 microng/ml. At low concentrations (10(-8)--10(-3) microng/ml) fragment I potentiates ACTH-induced steroidogenesis. Fragment I has no effect on the lipolysis;however, it potentiates ACTH-induced lipolysis at concentrations of 10--100 microng/ml. The results obtained support our previous supposition that "common" fragments are essential secondary non-specific active sites of hormones.