Bioactive peptides acting on animals and plants

Ala-Met-Lys-Pro-Trp是从酪蛋白消化液中分离得到的一种花粉管延伸肽，静脉注射后表现出较弱的升压活性。大鼠给药。当该肽的升压活性被血管紧张素-AT1拮抗剂阻断时，其花粉管伸展活性不受该拮抗剂的影响。大豆多肽是从大豆消化中分离得到的一种免疫刺激多肽，它通过fMLP受体发挥作用。大豆多肽-4(Met-Ile-Thr-Leu)是一种具有免疫刺激活性的小肽，可促进茶树花粉管的伸长。大豆多肽-4在不同长度的大豆多肽中，对花粉管和根伸长的刺激活性最高，似乎不是单纯的营养效应。上述酪蛋白衍生的ALA-Met-Lys-Pro-Trp也促进了根的伸长。虽然fMLP对花粉管伸长有微弱的刺激作用，但对根的伸长没有活性。大豆4号中的甲硫氨酸残基对免疫刺激和花粉管和根的伸长都是必需的。然而，在不同的大豆肽-4衍生物中，这三种活性最高的多肽是不同的，免疫刺激、花粉管伸长和根伸长的最佳多肽分别是MIWL、MRGG和M(O)TL。这些结果表明，介导这三种活动的受体是不同的，尽管细胞内钙水平升高是常见的受体后事件。

Ala-Met-Lys-Pro-Trp, which was isolated as a pollen tube-extending peptide from casein digest exhibited weak hypertensive activity after iv. administration in rats. While hypertensive activity of the peptide was blocked by an angiotensin AT1 antagonist, the pollen tube-extending activity was not affected by the antagonist.Soymetide which was isolated as an immunostimulating peptide from soybean digest acts through fMLP receptor. Soymetide-4 (Met-Ile-Thr-Leu), the minimum peptide to show immunostimulating activity promoted extension of tea pollen tube. It also stimulated extension of Brassica campestris root at 10^<-7>M.The activity seems to be not a mere nutritional effect since the extension was inhibited by the peptide above 10^<-4>M.Soymetide-4 exhibited the highest activity both for stimulation of pollen tube and root exyension among the soymetide fragment peptides of various length. Ala-Met-Lys-Pro-Trp derived from casein as descibed above also stimulated root extension. Although fMLP weakly stimulated pollen tube extension, it was inactive for root.Methioninyl residue in soymetide-4 was essential for both immunostimulation and extension of pollen tube and root. However, the peptide showing the maximum activity was different for these three activities among soymetide-4 derivatives ; the best peptide for immunostimulation, pollen tube extension and root extension was MIWL, MRGG and M (O) TL, respectively. These results suggest that receptors mediating these three activities are different each other though elevation of intracelullar calcium level is the common post-receptor event following them.