A comparative study of soluble calcium-dependent proteolytic activity in brain.
A comparative study of soluble calcium-dependent proteolytic activity in brain.
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脑中可溶性钙依赖性蛋白水解活性的比较研究。
DOI：
10.1002/neu.480170103
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Lynch,G
中科院分区：
文献类型：
--
作者：
Baudry,M;Simonson,L;Dubrin,R;Lynch,G
最近的研究表明，脑内可溶性钙活化蛋白酶（calpain）降解与细胞骨架相关的蛋白质，其活性在不同区域和发育过程中存在显著差异。这表明，观察到的钙蛋白酶活性的差异反映了结构元件周转率的差异。本研究通过测量五类脊椎动物的代表钙蛋白酶的性质和活性来扩展这一分析，特别强调哺乳动物。没有证据表明，在中性pH下，无论是否添加钙，鱼脑的可溶性部分都存在蛋白质水解。在两栖动物的大脑中发现了大量不依赖钙的蛋白水解活性——多种蛋白酶抑制剂的作用表明它也是一种中性硫醇（半胱氨酸）蛋白酶。爬行动物的大脑表现出钙不依赖型和钙依赖型蛋白水解活性。在中性pH下测量的鸟类（5种）和哺乳动物（9种）的蛋白质水解活性几乎都依赖于钙。钙活化蛋白酶的内源性底物在几种鸟类和哺乳动物中非常相似，各种蛋白酶抑制剂的作用也非常相似。然而，在哺乳动物中，每毫克可溶性蛋白表达的酶活性与脑大小呈高度负相关。这种关系的异速表达类似于大脑皮层神经元密度作为绝对大脑大小的函数。这些结果表明，在不同种类的脊椎动物中，脑中的可溶性蛋白水解酶的表达是不同的，并表明鸟类和哺乳动物的细胞骨架元素的周转在重要方面与鱼类和两栖动物不同。在哺乳动物中获得的结果提出了一种可能性，即在这种脊椎动物中，大脑的大小与结构元素被分解和替换的速度之间存在关系。
Recent studies have shown that soluble calcium activated proteases (calpains) in brain degrade proteins associated with the cytoskeleton and vary markedly in activity across regions and as a function of development. It was suggested that the observed differences in calpain activity reflect differences in the turnover rate of structural elements. The present study extends this analysis by measuring the properties and activity of calpain in representatives of the five classes of vertebrates with particular emphasis on the mammals.No evidence for proteolysis was found in soluble fractions of fish brains at neutral pH in the presence or absence of added calcium. A substantial calcium‐independentproteolytic activity was found in amphibian brains—the effects of a variety of protease inhibitors indicated that it is also a neurtral thiol (cysteine) protease. Reptilian brains exhibited both calcium‐independent and calcium‐dependent proteolytic activity. Virtually all proteolytic activity in birds (5 species) and mammals (9 species) measured at neutral pH was calcium‐dependent. The endogenous substrates for the calcium activated proteases were very similar in several species of birds and mammals as were the effects of a variety of protease inhibitors. However, the activity of the enzyme, expressed per mg of soluble protein, was highly and negatively correlated with brain size in the mammals. The allometric expression for this relationship was similar to that found for the density of neurons in cerebral cortex as a function of absolute brain size. These results indicate that soluble proteolytic enzymes in brain are differentially expressed among classes of vertebrates and suggest that the turnover of cytoskeletal elements in birds and mammals differs in important ways from that found in fish and amphibians. The results obtained for mammals raise the possibility of a relationship between brain size and the rate at which structural elements are broken down and replaced in this vertebrate class.