Analysis of sea urchin digestive system for the development artifical feed

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 16580140
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: General fisheries
• Research Institution: Hokkaido University
• Principal Investigator: SHIMIZU Motohiro Hokkaido Univ., Fac.of Fish.Sci., Associate Professor, 大学院・水産科学研究院, 助教授 (80002088)
• Co-Investigator(Kenkyū-buntansha): TAKAGI Yasuaki Hokkaido Univ., Fac.of Fish. Sci., Professor, 大学院・水産科学研究院, 教授 (10212002) ; OJIMA Takao Hokkaido Univ., Fac.of Fish. Sci., Professor, 大学院・水産科学研究院, 教授 (30160865) ; URA Kazuhiro Hokkaido Univ., Fac.of Fish. Sci., Instructor, 大学院・水産科学研究院, 助手 (90360940)
• Project Period (FY): 2004 – 2005
• Keywords: Sea urchin / Digestive system / Protease / Cellulases / Digestive enzyme / Echinoderms

Research Abstract

The sea urchin is an important coastal fisheries resource in Hokkaido. Unfortunately, they have been decrease in natural stocks, and therefore aquaculture techniques are required. In order to develop possible culture methods, physiological roles of digestive canal under artificial conditions should be revealed. However, there is little information on the fine structure and physiological roles of the digestive canal of the sea urchin. Following results were obtained.
1.The digestive canal of the sea urchin has following five parts, pharynx, esophagus, stomach, intestine and rectum. In the epithelium layer of the pharynx and esophagus, two types of granular cells stained with PAS and/or alcian blue were observed. Some granules observed in pharynx and esophagus were also stained with Hematoxylin. In epithelium layer of stomach, one type of granules were found. These granules were secreted in apical region of cytoplasm.
2.In order to obtain information about carnivorous actions of sea urchin , we investigated the occurrence of proteases in the sea urchin viscera and purified a major protease. N-terminal and internal amino acid sequences of the protease showed 37.9-55.2% identity to those of subtilisin-like alkaline serine protease, i.e. a subtilase. We determined the entire amino acid sequence of the protease using cDNAs amplified by PCR from cDNA library using degenerated primers. The mature sea urchin subtilase was considered to consist of 311 residues with calculated molecular mas of 32,270 Da. Primary structure of catalytic domain of the sea urchin subtilase showed 33-46% identity with those of bacterial subtilases such as subtilisin, proteinase K, and aqualysin.
3.In this study, we attempted to isolate and characterize a cellulose from sea urchin. A cDNA library from sea urchin digestive tracts was constructed and cDNA encoding SnEG54 were amplified by the PCR using degenerate primers designed from the partial amino acid sequences of SnEG54. By overlapping the amino acid sequence of 444 residues was deduced from the coding region. The amino acid sequence of mature SnEG54 showed 57, 55 and 51% identity with the corresponding regions of termite, sea squirt, and abalone cellulases, respectively.