Devi L, Goldstein A
Biochem Biophys Res Commun. 1985 Aug 15;130(3):1168-76. doi: 10.1016/0006-291x(85)91738-3.
Dynorphin B (rimorphin) is formed from dynorphin B-29 (leumorphin) by the action of a thiol protease from rat brain membranes. This represents a "single-arginine cleavage" between threonine-13 and arginine-14 of the substrate. In isotope dilution experiments we find that the radioactivity from radiolabelled dynorphin B-29, which appears in dynorphin B during incubation with the enzyme preparation, is not diminished by addition of a high concentration of dynorphin B-Arg14. Moreover, in pulse-chase experiments, radioactivity that appeared in dynorphin B-Arg14 did not decrease, nor did the radioactivity in dynorphin B increase, after chasing with a high concentration of non-radioactive dynorphin B-29. These results indicate that although some dynorphin B-Arg14 is formed by the impure enzyme preparation, it is not an intermediate in the conversion of dynorphin B-29 to dynorphin B. Thus the formation of dynorphin B does not involve the action of a trypsin-like enzyme followed by removal of arginine-14 by a carboxypeptidase B-like enzyme. It appears that a single enzyme converts dynorphin B-29 to dynorphin B in a single step.
强啡肽B（边缘强啡肽）是由大鼠脑膜中的硫醇蛋白酶作用于强啡肽B - 29（亮氨酸强啡肽）形成的。这代表底物苏氨酸 - 13和精氨酸 - 14之间的“单精氨酸切割”。在同位素稀释实验中，我们发现，在与酶制剂孵育期间出现在强啡肽B中的放射性标记强啡肽B - 29的放射性，不会因添加高浓度的强啡肽B - Arg14而降低。此外，在脉冲追踪实验中，用高浓度的非放射性强啡肽B - 29进行追踪后，出现在强啡肽B - Arg14中的放射性没有降低，强啡肽B中的放射性也没有增加。这些结果表明，虽然不纯的酶制剂会形成一些强啡肽B - Arg14，但它不是强啡肽B - 29转化为强啡肽B的中间体。因此，强啡肽B的形成不涉及类胰蛋白酶样酶的作用，随后也不涉及类羧肽酶B样酶去除精氨酸 - 14的过程。看来单一的酶一步就能将强啡肽B - 29转化为强啡肽B。
