Bassuk J A, Berg R A
Department of Biochemistry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854-5635.
Matrix. 1989 Jun;9(3):244-58. doi: 10.1016/s0934-8832(89)80057-5.
Protein disulphide isomerase (E.C. 5.3.4.1) has been purified, cloned, and sequenced from a variety of vertebrate tissues. The enzyme and its isoforms have been assigned a role in four functional activities: (1) hydroxylation of proline residues in procollagen; (2) disulphide bond oxidation, isomerization, and reduction; (3) the major non-nuclear binding protein of the thyroid hormone 3,3',5-triiodo-L-thyronine; and (4) a component of oligosaccharide transferase. The concentration of the enzyme has been shown to be positively correlated with an endoplasmic reticulum network which is active in secreting disulphide-bonded polypeptides. The enzyme is directed into the endoplasmic reticulum by virtue of a 19 residue N-terminal signal peptide; a four amino acid C-terminal KDEL sequence prevents the enzyme from being secreted. Careful inspection of the sequence data of the isoforms from human tissues reveals a 97% similarity; whereas, analyses of the data from chick tissues reveals only a 80% level of similarity. Chromosomal localizations using human cDNA probes against different human isoforms have assigned the gene(s) to opposite ends of the long arm of chromosome 17. The compiled data suggest the presence of a family of related polypeptides, all of which reside within the lumen of the endoplasmic reticulum.
蛋白质二硫键异构酶（E.C. 5.3.4.1）已从多种脊椎动物组织中纯化、克隆并测序。该酶及其同工型在四种功能活动中发挥作用：（1）前胶原中脯氨酸残基的羟基化；（2）二硫键的氧化、异构化和还原；（3）甲状腺激素3,3',5-三碘-L-甲状腺原氨酸的主要非核结合蛋白；（4）寡糖转移酶的一个组成部分。已证明该酶的浓度与在内质网网络中活跃分泌二硫键连接多肽的内质网网络呈正相关。该酶凭借一个19个残基的N端信号肽被引导进入内质网；一个四氨基酸的C端KDEL序列可防止该酶被分泌。仔细检查来自人类组织的同工型的序列数据发现相似度为97%；而对来自鸡组织的数据进行分析发现相似度仅为80%。使用针对不同人类同工型的人类cDNA探针进行染色体定位已将该基因定位到17号染色体长臂的两端。汇总的数据表明存在一个相关多肽家族，所有这些多肽都位于内质网腔中。
