Extensin is a glycoprotein that is rich in hydroxyprolines linked to ␤-L-arabinofuranosides. In this study, we cloned a hypBA2 gene that encodes a novel ␤-L-arabinobiosidase from Bifidobacterium longum JCM 1217. This enzyme does not have any sequence similarity with other glycoside hydrolase families but has 38 -98% identity to hypothetical proteins in Bifidobacterium and Xanthomonas strains. The recombinant enzyme liberated L-arabinofuranose (Araf)-␤1,2-Araf disaccharide from carrot extensin, potato lectin, and Araf-␤1,2-Araf-␤1,2-Araf-␤-Hyp (Ara 3 -Hyp) but not Araf-␣1,3-Araf-␤1,2-Araf-␤1,2-Araf-␤-Hyp (Ara 4 -Hyp) or Araf-␤1,2-Araf-␤-Hyp (Ara 2 -Hyp), which indicated that it was specific for unmodified Ara 3 -Hyp substrate. The enzyme also transglycosylated 1-alkanols with retention of the anomeric configuration. This is the first report of an enzyme that hydrolyzes Hyplinked ␤-L-arabinofuranosides, which defines a new family of glycoside hydrolases, glycoside hydrolase family 121.

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A survey of the concentration of carbon monoxide (CO) in flesh from a variety of fish was conducted to see whether fish which had been exposed to CO gas could be detected. CO in fish flesh was obtained by head-space gas chromatography and determined after conversion of CO to methane with a methanizer. Concentrations of CO ranged from 3 to 12jg/kg fish flesh, showing a narrow range in each species of fish except tilapia (Tilapia mossambica). CO was high in the red-flesh fish and low in the white-flesh fish. CO in sliced tilapia (a species of white-flesh fish), however, ranged from 7 to 957jg/kg. In tilapia, a high concentration of CO was observed in a sample in which the blood-colored parts of the slice were bright red, whereas the CO concentration was low in a sample in which the blood-colored parts were dark brown. The CO concentration in sliced tilapia containing Big CO/kg increased to 234jg/kg when the slice was exposed to CO gas. The blood-colored parts of the slice became bright red after the exposure. CO in the homogenate prepared from the CO-exposed sample decreased to less than 50jg/kg within 4 days on storage in a refrigerator (5C). The concentration of CO in the control increased slightly during this period. Among 19 commercial samples of tilapia, CO slightly increased in 5 samples containing about 10jig CO/kg and decreased in 14 samples containing more than 50 jig CO/kg when the homogenate was kept at 5C for 2 days. The blood-colored parts of the former group containing lower concentrations of CO were dark brown and those of the latter group containing higher concentrations of CO were bright red. The latter group of tilapia was suspected to have been exposed to CO gas.

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