6533b821fe1ef96bd127b6aa

RESEARCH PRODUCT

Molecular and kinetic properties of lactate dehydrogenase in the degenerating peripheral nerve

subject

description

Abstract Electrophoretic and catalytic studies have been carried out on lactate dehydrogenase of normal and transected sciatic nerves of the rat. Lactate dehydrogenase of the intact nerve exhibits an almost even distribution of activity among its component iso-enzymes. The complete transection of the nerve is responsible for a deep and immediate shift of the enzyme towards the so-called muscle type pattern. Seven days after the nerve section the percentage activity of iso-enzyme 5 is almost three times higher than in the intact nerve. After a short lag period lactate dehydrogenase specific activity (activity/mg protein) undergoes a sharp decrease in transected nerves. The return of the electrophoretic composition of the enzyme to a pattern similar to that of the intact nerve is not paralleled by any subsequent modification of specific activity. Some kinetic properties of the enzyme have shown changes parallel to those revealed by the electrophoretic analysis. The inhibition by excess lactate has exhibited, in fact, an increase and a subsequent decrease, which have been in keeping with the observed changes in the percentage activity of iso-enzyme 5 and related hybrid forms. Other kinetic parameters, such as the affinity for the substrates, have not shown significant modifications. The relationships of these neurochemical findings to the quantitative cytology of nerve degeneration and the metabolic significance of changes in the iso-enzymic patterns of lactate dehydrogenase are discussed.