Suitability of naphthyl-?-l-fucosides for the investigation of ?-l-fucosidases

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Abstract
In comparison with 1- and 2-naphthyl β-d-glucoside, β-d-galactoside, β-d-glucuronide, β-d-N-acetylglucosaminide, α-d-glucoside, α-d-galactoside and α-d-mannoside 1- and 2-naphthyl α-l-fucoside are hydrolyzed more quickly or to the same extent by homogenates prepared from freezedried cryostate sections of various rat organs. Nevertheless, when the fucosides are employed for the histochemical demonstration of α-l-fucosidase mostly negative data were obtained independent on the method used, whereas all other naphthyl glycosides deliver positive results. The reasons for these discrepancies are the marked inhibition of α-l-fucosidase by aldehyde fixation and diazonium salts. Then, α-l-fucosidase activity is suppressed to 90% and between 85 and 98% respectively; the inhibition of α- and β-d-glucosidase, α- and β-d-galactosidase, α-d-mannosidase, β-d-glucuronidase and β-d-N-acetylglucosaminidase by the fixative or coupling reagent does not exceed 70%. Therefore 1- and 2-naphthyl α-l-fucoside cannot be recommended in general for histochemical purposes. Small amounts of dimethylformamide do not influence the activity of most of the glycosidases investigated. For biochemical measurements, however, especially 1-naphthyl α-l-fucoside represents a suitable alternative in a fluorometric procedure instead of p-nitrophenyl α-l-fucoside used for the photometric evaluation of α-l-fucosidase. With the fluorometric method the enzyme was measured in rat organs, which posses remarkably different activities of α-l-fucosidase. Verglichen mit 1- und 2-Naphthyl-β-d-glucosid,-β-d-galactosid,-β-d-glucuronid,-β-d-N-acetylglucosaminid,-α-d-glucosid,-α-d-galactosid und-α-d-mannosid werden 1- und 2-Naphthyl-α-l-fucosid schneller oder im gleichen Ausmaß von Homogenaten verschiedener Rattenorgane hydrolysiert. Trotzdem fällt der histochemische Nachweis der α-l-Fucosidasen methodenunabhängig im Gegensatz zu dem der anderen Glykosidasen überwiegend negativ aus. Ursache dafür ist die massive Hemmung der α-l-Fucosidase durch Aldehydfixation und Diazoniumsalze; die Inhibitionsrate liegt bei 90% bzw. zwischen 85 und 98%; die α- und β-d-Glucosidase, α- und β-d-Galactosidase, α-d-Mannosidase, β-d-Glucuronidase sowie β-d-N-Acetylglucosaminidase werden durch Aldehydfixation oder Kuppler höchstens zu 70% gehemmt. Daher können 1- und 2-Naphthyl-α-l-fucosid für die histochemische Darstellung der α-l-Fucosidase nicht einschränkungslos empfohlen werden. Kleine Mengen Dimethylformamid hemmen die meisten Glykosidasen nicht. Für biochemische Messungen der α-l-Fucosidase eignet sich speziell 1-Naphthyl-α-l-fucosid und läßt sich an Stelle von p-Nitrophenyl-α-l-fucosid werwenden. Bei der fluorometrischen Untersuchung der α-l-Fucosidase in Rattenorganen mit dem 2-Naphthylderivat ergeben sich bemerkenswerte Aktivitätsunterschiede.

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