| Autor: |
Ghoda, L Y, Savarese, T M, Dexter, D L, Parks, R E, Trackman, P C, Abeles, R H |
| Zdroj: |
Journal of Biological Chemistry; June 1984, Vol. 259 Issue: 11 p6715-6719, 5p |
| Abstrakt: |
5'-Deoxy-5'-methylthioadenosine (methylthioadenosine) is cleaved to adenine and 5-methylthioribose-1-phosphate (methylthioribose-1-P). Methylthioribose-1-P is converted to 2-keto-4-methylthiobutyrate ( ketomethylthiobutyrate ) which is transaminated to methionine. We report that one subline of a heterogeneous human colon carcinoma, DLD-1 Clone D, only forms methylthioribose-1-P from methylthioadenosine or 5'-deoxy-5'-methylthioinosine (methylthioinosine), a deaminated derivative of methylthioadenosine, whereas Clone A converts methylthioadenosine and methylthioinosine to methionine, as shown by growth studies in culture of Clone A and Clone D cells and radioactive studies utilizing [methyl-14C]methylthioadenosine or [methyl-14C]methylthioinosine in the presence of extracts of these cells lines. To characterize this defect, we utilized three protein fractions isolated from rat liver which together convert methylthioribose-1-P to ketomethylthiobutyrate . Addition of only Fraction A to Clone D sonicates restores its ability to convert methylthioadenosine to methionine. This fraction is responsible for converting methylthioribose-1-P to 5- methylthioribulose -1-phosphate; radioactive studies confirm this observation. Thus, Clone D is deficient in an enzyme contained in Fraction A; this represents a qualitative biochemical difference between the two clones derived from a single human tumor. |
| Databáze: |
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