ISSN:
1573-4943
Keywords:
Lens crystallin
;
ε-crystallin
;
lactate dehydrogenase
;
enzyme kinetics
;
isozyme electrophoresis
;
eye lens
;
duck
;
caiman
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Kinetic comparison of ε-crystallins isolated from the avian and reptilian species and the authentic lactate dehydrogenases (LDHs) was undertaken in order to clarify the identities of these structural lens proteins in relation to their enzymatic activity. Caiman ε-crystallin similar to the previously characterized duck ε-crystallin appeared to possess a genuine and stable LDH activity as detected by nitro blue tetrazolium staining on polyacrylamide gels and conventional kinetic assays. Kinetic parameters for pyruvate,l-lactate, NAD+, and three structural analogues of the coenzyme in this ε-crystallin catalyzed reaction were also determined and compared. Despite the structural similarities between ε-crystallins and chicken heart LDH, differences in charge and kinetic properties have been revealed by native isozyme electrophoresis and kinetic analysis as examined by initial velocity and substrate inhibition studies. It is found that the kinetic data analyzed for caiman ε-crystallin were more fitted with a compulsory ordered Bi-Bi sequential mechanism similar to those for the authentic LDHs and duck ε-crystallin. Caiman ε-crystallin has for the first time been established as a heart-type LDH based on the kinetic analysis and comparison with the authentic heart- and muscle-type LDHs from pig and chicken.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01024779
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