進行性筋ジストロフィー症骨格筋におけるmyoglobinの異常

Abnormality of Myoglobin in Duchenne Type of Progressive Muscular Dystrophy

I．はじめに

　ミオグロビンmyoglobin（以下Mb）は，1コのヘムと約150コのアミノ酸残基からなる1本のpolypeptide鎖でできている。分子量は約17,000である。これらの成績は主としてクジラMbについてえられたもので，これに関するKendrewら^1）のX線解析法による研究は，蛋白質の立体構造の解明に先鞭をつけたものとして耳目に新しい。

　生理的には，血上色素よりも酸素親和性が強く，筋内に酸素を一時的に貯蔵する。すなわち，その構造，機能の上からは，血色素に類似するが，筋の代謝生理に果たす役割の詳細については明らかではない。またその異常型の存在についても確定的なことは不明である。

On the myoglobin (Mb) obtained by Singer'smethod from the biopsied muscle of the pa-tients with progressive muscular dystrophy(PMD), spectrophotometric examinations andelectrophoretic studies were made by thepresent authors.

Spectrophotometry in the visible regionrevealed no recognizable differences in theabsorption curves between the met-Mb fromthe patients with PMD and that from cotrols.However, in the ultraviolet region in Duche-nne type of PMD, the maximum of the abso-rption at pH 7.0 was approximately at 275mμin contrast to 281mμ in normal controls, neu-rogenic muscular atrophy and other types ofPMD.

The electrophoretic studies using celluloseacetate membrane and Cyanogum gel revealedthat the Mb of normal controls could be sepa-rated into four subfractions, Mb₁, Mb₂, Mb₃, andMb₄, being predominated by Mb₁ among thefour. But, in Duchenne type of PMD, Mb₁decreased markedly and Mb₃ increased relati-vely. This abnormal electrophoretic patternof Mb subtraction was not recognized in Mbof normal and other controls. Absorption ma-xima in the ultraviolet region of Mb₃ and Mb₄usually shifted to the blue in contrast to thoseof Mb₁ and Mb₂ at 281mμ, and the characteristicchanges of Mb of Duchenne type of PMD areconsidered to be ascribed to the decrease ormalformation of Mb₁ and a relative increaseof Mb₃.

It is of interest to presume that the sub-fractions of Mb in the Duchenne type of PMDare so modified in amino acid composition orin three dimensional structures of protein ascompared with those of normal Mb.