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Neuraminidase in Calf Retinal Outer Segment Membranes
Author(s) -
Dreyfus H.,
Preti A.,
Harth S.,
Pellicone C.,
Virmaux N.
Publication year - 1983
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1983.tb12669.x
Subject(s) - neuraminidase , glycoconjugate , ganglioside , biochemistry , sialidase , sialic acid , glycoprotein , enzyme , endogeny , membrane , biology , hydrolysis , chemistry
An enzyme catalyzing the hydrolysis of sialic acid ( N ‐acetylneuraminic acid: NeuNAc)‐containing glycoconjugates has been found in bovine retinal rod outer segment (ROS) membranes. The enzymatic activity is optimal at pH 4.0 and is stimulated by 0.15% Triton X‐100. Total activity was determined by the release of NeuNAc from endogenous and exogenous substrates (GDla). The ROS enzyme preferentially hydrolyses the ROS gangliosides, possibly because they are more accessible than the glycoproteins as substrates for the neuraminidase. Release of NeuNAc from gangliosides leads to important changes in the ganglioside patterns; whereas the amounts of GM1 increased throughout the incubation, the levels of polysialogangliosides GTlb and GD3 diminished owing to their rapid hydrolysis. The finding that gangliosides are hydrolysed more extensively than glycoproteins suggests that endogenous ROS gangliosides may be the principal source of metabolically available sialic acid in ROS. It was also observed that the activity of ROS neuraminidase is not affected by illumination of the membranes.