Tereshchenkova Valeriia F, Goptar Irina A, Zhuzhikov Dmitry P, Belozersky Mikhail A, Dunaevsky Yakov E, Oppert Brenda, Filippova Irina Yu, Elpidina Elena N
Chemical Faculty, Lomonosov Moscow State University, Moscow, Russia.
Biological Faculty, Lomonosov Moscow State University, Moscow, Russia.
Arch Insect Biochem Physiol. 2017 Aug;95(4). doi: 10.1002/arch.21395. Epub 2017 Jun 29.
Prolidase is a proline-specific metallopeptidase that cleaves imidodipeptides with C-terminal Pro residue. Prolidase was purified and characterized from the Tenebrio molitor larval midgut. The enzyme was localized in the soluble fraction of posterior midgut tissues, corresponding to a predicted cytoplasmic localization of prolidase according to the structure of the mRNA transcript. Expression of genes encoding prolidase and the major digestive proline-specific peptidase (PSP)-dipeptidyl peptidase 4-were similar. The pH optimum of T. molitor prolidase was 7.5, and the enzyme was inhibited by Z-Pro, indicating that it belongs to type I prolidases. In mammals, prolidase is particularly important in the catabolism of a proline-rich protein-collagen. We propose that T. molitor larval prolidase is a critical enzyme for the final stages of digestion of dietary proline-rich gliadins, providing hydrolysis of imidodipeptides in the cytoplasm of midgut epithelial cells. We propose that the products of hydrolysis are absorbed from the luminal contents by peptide transporters, which we have annotated in the T. molitor larval gut transcriptome. The origin of prolidase substrates in the insect midgut is discussed in the context of overall success of grain feeding insects.
脯氨酰二肽酶是一种特异性作用于脯氨酸的金属肽酶，可切割C端为脯氨酸残基的亚氨基二肽。从黄粉虫幼虫中肠中纯化并鉴定了脯氨酰二肽酶。该酶定位于中肠后部组织的可溶性部分，根据mRNA转录本的结构，这与脯氨酰二肽酶预测的细胞质定位相对应。编码脯氨酰二肽酶和主要消化性脯氨酸特异性肽酶（PSP）——二肽基肽酶4的基因表达相似。黄粉虫脯氨酰二肽酶的最适pH为7.5，该酶受Z-脯氨酸抑制，表明它属于I型脯氨酰二肽酶。在哺乳动物中，脯氨酰二肽酶在富含脯氨酸的蛋白质——胶原蛋白的分解代谢中尤为重要。我们提出，黄粉虫幼虫脯氨酰二肽酶是膳食中富含脯氨酸的醇溶蛋白消化最后阶段的关键酶，可在中肠上皮细胞的细胞质中水解亚氨基二肽。我们提出，水解产物通过肽转运体从肠腔内容物中吸收，我们已在黄粉虫幼虫肠道转录组中注释了这些转运体。在谷物取食昆虫总体成功的背景下，讨论了昆虫中肠中脯氨酰二肽酶底物的来源。
