A re-evaluation of the molecular size of duck epsilon-crystallin and its comparison with avian lactate dehydrogenases.
A biochemical comparison of epsilon-crystallin isolated from the duck lens and lactate dehydrogenases of chicken heart has been made in order to establish the structural and functional identities of these two proteins. The native molecular weight of epsilon-crystallin was re-examined by combining sedimentation and gel-filtration data. It was found that epsilon-crystallin is 150 kDa in contrast to the 120 kDa reported previously for this crystallin. Subunit cross-linking experiments corroborated that lactate dehydrogenase and epsilon-crystallin both exist as tetramers of four identical subunits in their native quaternary structures. Amino acid compositions plus N-terminal analyses revealed no differences between the two proteins. Duck epsilon-crystallin exhibited high enzymatic activity of lactate dehydrogenases even after a long period of storage, and showed characteristic thermostability at 50 degrees C for several hours. Comparison of the enzyme activity of duck lens homogenate with those of heart, liver and muscle tissues revealed that duck lens is a much richer source than other tissues for the isolation and characterization of this important enzyme which appears also as a structural protein in the lens.
Chiou
S H
SH
Institute of Biochemical Sciences, National Taiwan University, China.
Chang
W P
WP
Lin
H K
HK
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents; D003459:Crystallins / Q000648:ultrastructure*; D004372:Ducks; D007770:L-Lactate Dehydrogenase; D046911:Macromolecular Substances; D008970:Molecular Weight
D003432:Cross-Linking Reagents; D003459:Crystallins; D046911:Macromolecular Substances; D007770:L-Lactate Dehydrogenase