Erythrocyte membrane Na+,K+-ATPase and Mg2+-ATPase activities in subjects with methylenetetrahydrofolate reductase (MTHFR) 677 C-->T genotype and moderate hyperhomocysteinaemia. The role of L-phenylalanine and L-alanine.

BACKGROUND: Increased homocysteine (Hcy) blood levels are correlated with vascular and neurological problems. The aim of our study was to investigate erythrocyte membrane Na(+),K(+)-ATPase and Mg(2+)-ATPase activities in patients with methylenetetrahydrofolate reductase (MTHFR) 677 C-->T genotype. METHODS: Blood was obtained from 25 patients before and after folic acid supplementation and from controls (n=30) once. Plasma folate, vitamin B(12) and total antioxidant status (TAS) were measured using commercial kits, Hcy was determined by HPLC and membrane enzyme activities were measured spectrophotometrically. RESULTS: Mg(2+)-ATPase remained unaltered. Membrane Na(+),K(+)-ATPase activity was remarkably increased in patients (0.77+/-0.06 micromol Pi/h x mg protein) and decreased to normal levels (0.52+/-0.05 micromol Pi/h x mg protein; p<0.001) after therapy. TAS did not differ significantly before and after treatment. Hcy levels were significantly higher before therapy (25.4+/-2.8 micromol/L) than levels after therapy (12.1+/-2.0 micromol/L; p<0.001) and in controls (10.5+/-2.5 micromol/L, p<0.001). In vitro, L-phenylalanine (Phe) reversed to normal the stimulated enzyme from patients before therapy. In addition, Phe incubation of the Hcy activated membrane Na(+),K(+)-ATPase from controls resulted in restoration of its activity, whereas L-alanine (Ala) incubation protected the enzyme from Hcy activation. CONCLUSIONS: The increased membrane Na(+),K(+)-ATPase activity may be due to high -SH group Hcy levels. In vitro, Phe reversed the increase in enzyme activity induced by Hcy in controls, as well as the stimulated membrane enzyme in untreated patients. Ala protected the enzyme from Hcy action.

Erythrocyte membrane acetylcholinesterase activity in subjects with MTHFR 677C-->T genotype.

BACKGROUND: Increased homocysteine (Hcy) blood levels are correlated with vascular and neurological problems. AIM: The aim of the present study was to investigate erythrocyte membrane acetylcholinesterase (AChE) activity in subjects with the MTHFR C677T genotype in relation to Hcy. METHODS: Blood was obtained from 22 individuals with the MTHFR C677T genotype before and after folic acid supplementation and once from controls (n = 30). Plasma folate, vitamin B(12) and total antioxidant status (TAS) were measured with commercial kits, Hcy by a HPLC method and membrane enzyme activity spectrophotometrically. RESULTS: In MTHFR C677T carriers, AChE activity was significantly higher (4.20 +/- 0.12 x mg protein) and decreased to normal levels (3.14 +/- 0.10 x mg protein; p < 0.001) after therapy. TAS differed slightly before and after treatment. Hcy levels were significantly higher before (22.4 +/- 2.8 microM) compared to after (12.1 +/- 2.0 microM; p < 0.001) therapy and compared to controls (10.5 +/- 2.5 micromol/L; p < 0.001). In an in vitro study, incubation of Hcy-activated membrane AChE from controls with phenylalanine resulted in restoration of activity, but failed to reverse the stimulated enzyme from hyperhomocysteinaemic MTHFR C677T subjects before therapy. Alanine incubation protected the enzyme from Hcy activation in controls. CONCLUSIONS: Increased membrane AChE activity may be due to high Hcy levels. In vitro, phenylalanine reversed the Hcy activation of the membrane enzyme from controls and alanine protected it from Hcy action.