市販β-NAD⁺標品中不純物質によるヒトLDHアイソザイムのサブバンド形成

抄録

When human lactate dehydrogenase, LDH (L-lactate: β-NAD⁺ oxidoreductase, EC 1. 1.1.27) was incubated with β-NAD⁺, five bands consisting of original band and four subbands were formed in each isozyme fraction of LDH₁(B₄), LDH₂(B₃A), LDH₃(B₂A₂), LDH₄(BA₃), and LDH₅(A₄), and at the same time LDH activity of the reaction mixture decreased with increase in the subband formation.
The subbands formed differed in their number, mobility, and the ratio of each band considerably depending on the commercial NAD⁺ samples used. The decrement of the activity also depended on them. These two characteristic changes also depended a great deal on the kind and pH of the buffers used.
The result obtained led us to conclude that the changes mentioned above were produced by some interfering substance contaminated in the NAD⁺ samples which bound each subunit in LDH tetramer in one to one ratio, maximally binding all of the four subunits.