Welinder K G, Mazza G
Eur J Biochem. 1975 Sep 15;57(2):415-24. doi: 10.1111/j.1432-1033.1975.tb02316.x.
Four isoperoxidases of turnip root and isoperoxidase C of horseradish root were digested with trypsin, and their peptide maps, prepared by high-voltage paper electrophoresis, were compared. All five tryptic digests were completely soluble at pH 8. The maps were developed with a variety of general and specific reagents: ninhydrin, histidine, tyrosine, tryptophan and arginine reagents. Cystine peptides and cysteic acid derivatives have also been characterized. All detected half-cystine residues seemed engaged in disulfide bridges. For each individual peroxidase the number of specifically staining peptides agreed very well with the amino acid composition. The two most acidic peroxidases of turnip, P1 and P2, only differ significantly in one peptide. The P2 gene is tentatively proposed to have developed from the P1 gene by a single base mutation, changing an asparagine residue to alysine residue. A less acidic turnip peroxidase, P3, is distinct, although related to peroxidases P1 and P2. Horseradish isoperoxidase C also belongs to this group which appears to be closely related in the amino acid sequences around four disulfide bridges. Peroxidase P7 differs from this group, at least around two of its disulfide bridges, and therefore, may differ from the other four in parts of its three dimensional structure. Sequences of particular importance to peroxidase function must be present in all peroxidases. From the peptide mapping studies we only find two highly homologous sequences present in all five examined peroxidases. Both contain histidine. This finding corroborates previous suggestions of two histidine sequences near the peroxidase heme prosthetic group. The rules applied in relating peptides of different proteins are outlined, and the sources of errors in mapping of glycoproteins of high carbohydrate content (about 20%) are discussed in detail.
用胰蛋白酶消化芜菁根的四种过氧化物酶和辣根根的过氧化物酶C，并比较通过高压纸电泳制备的它们的肽图。所有五种胰蛋白酶消化产物在pH 8时完全可溶。用多种通用和特异性试剂显影肽图：茚三酮、组氨酸、酪氨酸、色氨酸和精氨酸试剂。还对胱氨酸肽和半胱氨酸衍生物进行了表征。所有检测到的半胱氨酸残基似乎都参与了二硫键的形成。对于每种单独的过氧化物酶，特异性染色肽的数量与氨基酸组成非常吻合。芜菁的两种酸性最强的过氧化物酶P1和P2仅在一个肽段上有显著差异。初步推测P2基因是由P1基因通过单个碱基突变发展而来，将一个天冬酰胺残基变为赖氨酸残基。一种酸性较弱的芜菁过氧化物酶P3虽然与过氧化物酶P1和P2相关，但却是独特的。辣根过氧化物酶C也属于这一组，该组在四个二硫键周围的氨基酸序列似乎密切相关。过氧化物酶P7至少在其二硫键中的两个周围与该组不同，因此，其三维结构的某些部分可能与其他四种不同。对过氧化物酶功能特别重要的序列必须存在于所有过氧化物酶中。从肽图研究中我们只发现两个高度同源的序列存在于所有五种检测的过氧化物酶中。两者都含有组氨酸。这一发现证实了先前关于过氧化物酶血红素辅基附近有两个组氨酸序列的推测。概述了关联不同蛋白质肽段所应用的规则，并详细讨论了高碳水化合物含量（约20%）的糖蛋白图谱绘制中的误差来源。
