Bioactive peptides acting on animals and plants

从酪蛋白消化液中分离得到的花粉管延伸肽ala - met - lys - protrp在iv次给药后表现出较弱的高血压活性。虽然该肽的降压活性可被血管紧张素AT1拮抗剂阻断，但其花粉管伸展活性不受拮抗剂的影响。Soymetide是一种从大豆消化液中分离得到的免疫刺激肽，通过fMLP受体起作用。大豆肽-4 （met - ile - 3 - leu）是显示免疫刺激活性最低的肽，促进了茶花粉管的延伸。在10^<-7>M处刺激了油菜根的伸长。在10^<-4>M以上，肽抑制了伸展，因此活性似乎不仅仅是营养作用。在不同长度的大豆肽片段中，大豆肽-4对花粉管和根伸展的刺激活性最高。上述酪蛋白衍生的Ala-Met-Lys-Pro-Trp也刺激了根的延伸。fMLP虽然对花粉管伸展有微弱的刺激作用，但对根无刺激作用。大豆蛋白酶-4中的蛋氨酸基残基对花粉管和根的免疫刺激和延伸都是必需的。然而，大豆肽-4衍生物在这3种活性中表现出最大活性的肽段不同；对免疫刺激、花粉管延伸和根延伸效果最好的肽分别是MIWL、MRGG和M (O) TL。这些结果表明，介导这三种活动的受体各不相同，但细胞内钙水平升高是它们共同的受体后事件。

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.