4-Thia-trans-2-alkenoyl-CoA derivatives: properties and enzymatic reactions

4-Thiaacyl-CoA analogues, in which the 4-methylene group is replaced by a thioether sulfur atom, represent new chromophoric substrates of acyl-CoA dehydrogenases and oxidase. The corresponding 4-thia-trans-2-enoyl-CoA products exhibit a strong new absorption band (extinction coefficient 22 mM-1 cm-1) that is red shifted from 312 to 338 nm upon binding to the medium-chain acyl-CoA dehydrogenase. 4-Thiaoctanoyl-CoA reduces the dehydrogenase several-fold slower than octanoyl-CoA, although in turnover it is dehydrogenated 1.5-fold faster. The redox potential of 4-thia analogues is some 30 mV more negative than that of their unsubstituted counterparts. 4-Thia-trans-2-enoyl-CoA derivatives are slowly hydrated by enoyl-CoA hydratase (EC 4.2.1.17) to the corresponding thiohemiacetal which fragments nonenzymatically to 1 equiv each of malonylsemialdehyde-CoA and alkanethiol. This fragmentation reaction might explain the release of methanethiol during the transamination pathway of methionine degradation. 4-Oxaoctanoyl-CoA is a much poorer substrate and kinetic reductant of acyl-CoA dehydrogenase and oxidase than the 4-thia analogue. The corresponding enoyl-CoA product is also fragmented by the hydratase, yielding butanol and malonylsemialdehyde-CoA. Thus, 4-heterosubstituted acyl-CoA derivatives provide new tools for the study of beta-oxidation enzymes.     

Cobalt-immunocytochemical identification of peptidergic neurons inCalliphora innervating central and peripheral targets

Brain Cell Biology - Certain neurons of the blowfly,Calliphora erythrocephala, show immunoreactivity to anti-gastrin/cholecystokinin (CCK) COOH terminal specific antisera. However, as is common to...     

Micropropagation of Raphanus sativus L. var. longipinnatus (Japanese radish) cv. Gungjung

Shoot cultures were established from seedling shoot tips of Raphanus sativus var. longipinnatus Bailey cv. Gungjung, (Japanese radish) cultured on a Murashige-Skoog medium supplemented with ca. 4.5–135 M kinetin or N⁶-benzyladenine. The latter cytokinin supported overall better growth, and 22.2 M was adopted for maintenance of established cultures. The nitrate: ammonium levels in the medium proved optimal for growth and shoot proliferation and both these parameters were significantly increased by addition of adenine sulfate or sodium phosphate. Rooting of excised shoots was achieved on auxin containing medium. Indole-3-butyric acid (ca. 5 or 10 M) also enhanced shoot growth. Plants were easily established in soil, appeared morphologically normal, and flowered.     

Interleukin-4 proliferative signal transduction involves the activation of a tyrosine-specific phosphatase and the dephosphorylation of an 80-kDa protein

Interleukin-4 (IL-4) is a cytokine that expresses its biological effects by binding to specific membrane receptors. Although the diverse biological properties of this molecule have been characterized extensively the biochemical mechanisms by which extracellular binding events lead to biological responses remain unclear. IL-4 can stimulate the proliferation of several hemopoietic cell types, and we have taken advantage of its ability to induce the growth of leukemic cell lines to investigate the role that protein phosphorylation events might play in IL-4 mitogenic signal transduction. We show that the addition of IL-4 to several leukemic cell lines of different origin causes the rapid dephosphorylation of an 80-kDa phosphoprotein (p80) from tyrosine residues. This event occurs in a dose-responsive manner closely correlating to that of biological activity, and both are blocked by an anti-IL-4-specific antiserum. The ability of sodium orthovanadate to prevent IL-4-induced dephosphorylation of p80 suggests that this event is mediated by a protein-tyrosine-phosphatase (EC 3.1.3.48). The importance of the role that tyrosine-specific dephosphorylation plays in mediating IL-4 mitogenic signal transduction is substantiated by the ability of sodium orthovanadate in cell culture to block effectively IL-4-induced proliferation at doses that enhance the proliferation stimulated by either granulocyte-macrophage colony-stimulating factor or interleukin-3.