Kinetic Parameters of FPGS With MTX as Substrate and Accumulation of MTX Polyglutamates in ALL and AML Patients
| Diagnosis . | Km . | Vmax . | Long Chain MTX Polyglutamates . | Long Chain MTX Polyglutamates as % of Total Polyglutamates . |
|---|---|---|---|---|
| . | (μmol/L) . | (pmol/mg/h) . | (pmol/107 cells) . | . |
| ALL | 48 | 14,450 | 9 | 90 |
| ALL | 23 | 1,065 | 12.7 | 66 |
| ALL | 47 | 1,832 | 16.3 | 86 |
| Lymphoid BC/CML | 45 | 6,600 | 30.8 | 88 |
| AML | 75 | 1,490 | 3.36 | 24 |
| AML | 83 | 2,030 | ND | ND |
| AML | 100 | 1,000 | ND | ND |
| Diagnosis . | Km . | Vmax . | Long Chain MTX Polyglutamates . | Long Chain MTX Polyglutamates as % of Total Polyglutamates . |
|---|---|---|---|---|
| . | (μmol/L) . | (pmol/mg/h) . | (pmol/107 cells) . | . |
| ALL | 48 | 14,450 | 9 | 90 |
| ALL | 23 | 1,065 | 12.7 | 66 |
| ALL | 47 | 1,832 | 16.3 | 86 |
| Lymphoid BC/CML | 45 | 6,600 | 30.8 | 88 |
| AML | 75 | 1,490 | 3.36 | 24 |
| AML | 83 | 2,030 | ND | ND |
| AML | 100 | 1,000 | ND | ND |
Cells extracts were prepared as described in Materials and Methods. MTX at different concentrations was used to measure enzyme activity and to determine Km and Vmax values. Polyglutamates formation was measured after 24-hour exposure to radiolabeled MTX as described in Materials and Methods.
Abbreviation: ND, not done (insufficient sample).