A comparative study of methionine adenosyltransferase activity and regional distribution in mammalian spinal cord.

To provide a background for future studies on neurodegenerative changes in the spinal cord, the present study analysed the distribution of the activity of methionine adenosyltransferase (ATP:L-methionine S-adenosyltransferase, EC 2.5.1.6, MAT), an enzyme that catalyses the synthesis of the biological methyl group donor S-adenosylmethionine (AdoMet), in spinal cords from bovine and pig, and compared the results with those from human spinal cord. The enzyme activity was estimated by a radiochemical method measuring the rate of formation of [(3)H]AdoMet from L-[methyl-(3)H]methionine and ATP. The MAT activity (V(max)) was quite homogeneously distributed between spinal regions and species investigated (19-50 pmol [(3)H]AdoMet/mg protein/minute), with the highest level found in the male bovine group. The bovine group (both males and females) also presented a 20% higher enzymatic activity in the dorsal horn as compared to the ventral horn and white matter areas. In the pig spinal cord, the highest level of activity was found in the white matter. The lowest affinity for methionine (highest K(m)) was found in the human spinal cord. Whole spinal cords of one cat and one rhesus monkey were also analysed and the levels of MAT activity were similar to that of humans and bovine females, respectively. Studies of MAT stability in the rat spinal cord (post-mortem time 0-72 hr) showed a significant decrease in enzyme activity during the interval of 0-8 hr (23 degrees ). From this time point on and up to 72 hr (4 degrees ), the significant decrease in the activity remained at 60% of the initial value.

Upregulation of Bax protein and increased DNA degradation in ALS spinal cord motor neurons.

OBJECTIVES: To investigate if degeneration of motor neurons in amyotrophic lateral sclerosis (ALS) is related to altered levels of the apoptosis regulating proteins Bcl-2 and Bax. In addition, immunoreactivity of the cysteine protease ICH-IL and detection of motor neurons with DNA fragmentation, indicative of apoptosis, was also studied. MATERIAL AND METHODS: The immunoreactivity of Bcl-2, Bax and ICH-1L were compared in ALS and control spinal cord motor neurons by immunohistochemical analysis and motor neurons with DNA fragmentation were identified by the TUNEL-method. RESULTS: The results demonstrate an increased expression of Bax in the ALS material as compared to controls but no change in Bcl-2 and ICH-1L expressions. Moreover, a larger proportion of motor neurons stained positive for TUNEL in ALS spinal cords. CONCLUSION: Present study suggest an upregulation of the cell death promoting protein Bax and increased DNA degradation, indicative of apoptosis, in spinal motor neurons of ALS patients.

Methionine adenosyltransferase activity in erythrocytes and spinal cord of patients with sporadic amyotrophic lateral sclerosis.

The role of transmethylation mechanisms in the etiology of amyotrophic lateral sclerosis (ALS) is hitherto unexplored. The activity of L-methionine S-adenosyltransferase (MAT), a regulatory enzyme of S-adenosylmethionine biosynthesis, was investigated in erythrocytes of 21 patients with ALS, spinal cord specimens of 7 ALS patients, and matched controls. In ALS patients the activity of MAT in erythrocytes was sex-dependent. In comparison with controls, the male group presented a 33% higher V(max) (P < 0.05) and a 41% decrease in the affinity of MAT for methionine (K(m), P < 0.05). The type of ALS onset (limb or bulbar), age, or duration of the disease did not influence erythrocyte MAT activity. In the spinal cord, the activity of MAT was homogeneously distributed through dorsal horn, ventral horn, and white matter. Comparisons between data from controls and ALS patients and analysis of sex effect showed no significant differences. The kinetic difference of erythrocyte MAT in the male group of ALS patients might be interesting to explore since it is well known that there is a male predominance of 1.5 to 2. 5:1 in ALS.