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Electron microscopy of glycogen degrading enzymes
Author(s) -
Scraba Douglas G.,
Bradley Roger D.,
Fitzgerald Paula M.D.,
Madsen Neil B.
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)80354-5
Subject(s) - glycogen phosphorylase , electron microscope , glycogen , glycogen debranching enzyme , dimer , chemistry , enzyme , monomer , microscopy , glycogen branching enzyme , crystallography , biochemistry , optics , organic chemistry , physics , polymer
Single molecules of glycogen phosphorylase b exhibit images in the electron microscope which are similar in shape and dimension to those derived from X‐ray crystallography. Phosphorylase a exhibits tetramers but shows dimers in the presence of glucose. Glycogen debranching enzyme appears as a monomer with an unusual crescent or shrimp‐like shape, with occasional isologous aggregation to circular dimers. The longest dimension of the monomer is very similar to that of the phosphorylase dimer, 11.5 nm. Strong binding of the debranching enzyme to glycogen is readily visualized in the electron microscope. It is suggested that the distinctive shape of the debranching enzyme may be related to its catalytic function.