Two unrelated 16-year-old boys had mental retardation, cardiomegaly, and proximal myopathy. One also had hepatomegaly. Histochemistry and electronmicroscopy of muscle biopsies showed lysosomal glycogen storage resembling acid maltase deficiency. Biochemical studies of skeletal muscle showed increased content of glycogen of normal structure; acid alpha-glucosidase activity in both urine and muscle was normal. Other enzymes of glycogen metabolism were also normal. The cause of this apparently generalized glycogenosis with no demonstrable enzyme defect is unknown.
A girl with congenital limb weakness, mental retardation, and corneal ulceration died with respiratory insufficiency at age 4 years. Histochemistry of muscle biopsy showed only nonspecific myopathy, but electronmicroscopy revealed subsarcolemmal and intramyofibrillar accumulation of glycogen. Biochemical studies showed increased glycogen content of muscle with lack of phosphofructokinase. Phosphorylase b kinase activity was about 30% of normal. The relationship of the double enzyme deficiency to this unusual clinical picture is unclear.
The 31P NMR proton-decoupled spectra of alpha, beta-methylene-ATP [Ap(CH2)pp], beta, gamma-methylene-ATP [App(CH2)p], and alpha, beta-methylene-ADP [Ap(CH2)p] were measured as functions of pH and Mg2+ concentration. Each ATP analogue yielded three resonances: two doublets and one doublet-of-a-doublet. Assignments of resonances were based upon spin-coupling multiplets, their coupling constant magnitudes (24-27 Hz for -P-O-P- and 4-10 Hz for -P-CH2-P-), and the magnitude of the chemical shift movement during proton titration or its direction of movement. All phosphonyl resonances are substantially downfield compared to phosphoryl resonances. The chemical shifts of terminal phosphonyl units moved upfield with increasing pH or rising Mg2+ concentration. The chemical shifts of phosphonyl and phosphoryl anhydride plus ester units usually either moved downfield during proton titration and addition of Mg2+ or remained constant. Accurate pKa' values were readily determined from chemical shift movements as a function of pH: 3.05 +/- 0.04 and 8.80 +/- 0.05 for App(CH2)p, 7.34 +/- 0.06 for Ap(CH2)pp, and 8.29 +/- 0.02 for Ap(CH2)p. Addition of Mg2+ or Tris produced an acidic shift of the alkaline pKa' values. Addition of Mg2+ at pH 7.0 to the nucleotides caused large movements in the chemical shifts of their terminal two phosphorus atoms.
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