Partial purification and characterization of an insulin-like material from XXXX and Lemna gibba G3.

@entity1 @entity2772 @entity1042 @entity1573 @entity35 @entity413
The existence in invertebrates, unicellular eukaryotes, and prokaryotes of materials that resemble several vertebrate peptide hormones led to the suggestion that these peptide messengers may have arisen earlier in evolution than had previously been thought. Consistent with this hypothesis, we describe here material in two plants, @entity2772 and Lemma gibba G3, that is very similar to @entity1 insulin, yet distinctive. In each of the early purification steps, which consisted of acidic @entity1042 chloroform extraction and sequential chromatography on C-18 hydrophobic resin, Sephadex G-50, CM-Sepharose, and a short C-3 high performance liquid chromatography column, the immunoactive material from plants resembled the common vertebrate insulins. The protein nature of the material was suggested by its destruction by Pronase but not by the inactivated enzyme. In addition, on TSK chromatography it eluted in a position similar to that of insulin, i.e. equivalent to a protein of 6000 daltons. Using an isocratic high performance liquid chromatography system, the plant immunoactivity eluted earlier, and thus was more hydrophilic, than most of the common @entity1 insulins, including pork insulin. The interaction of the plant material with anti-insulin antibodies in a radioimmunoassay was confirmed by using an affinity column of anti-insulin antibodies which adsorbed the plant immunoactivity at neutral pH, and released the material with acid elution. Using a quantitative double radioimmunoassay, the plant insulin-like material was distinguished immunologically from @entity1573 insulin. Although the plant insulin-like material is clearly distinct from pork insulin chromatographically, and from @entity1573 insulin immunologically, it resembles vertebrate insulins in its overall configuration. The plant insulin-like material bound to insulin receptors on IM-9 lymphocytes and stimulated @entity413 oxidation and lipogenesis in isolated adipocytes from young @entity35 . The bioactivity was neutralized in the presence of anti-insulin antibodies, but not in the presence of normal guinea pig IgG. The role of this insulin-like material in plants is unknown but its existence is consistent with an early evolutionary origin of the insulin messenger peptide family. Alternatively we cannot exclude a later convergent development of this family or introduction of vertebrate DNA into plants.
