TABLE 3.
Activities of various enzymes in human islets compared with rat islets or INS-1 832/13 cells
Results are the mean ± S.E. of the number of samples from individual donors or batches of rat islets or individual plates of INS-1 832/13 cells studied and shown in parentheses. The mean ± S.E. BMI and age of the human islet donors whose islets were used for the ATP citrate lyase measurements were 32.4 ± 2.6 kg/m2 and 48.1 ± 3.6 years.
| Enzyme | Enzyme activity |
||
|---|---|---|---|
| Human islets | Rat islets | INS-1 832/13 | |
| nmol product/min/mg protein | |||
| ATP citrate lyasea | 24 ± 1.9 (21)d | 96 ± 9.0 (13) | 104 ± 3.5 (31) |
| mGPDc | 29 ± 2.2 (16) | 28 ± 1.5 (7) | 43 ± 2.8 (9) |
| Cytosolic ME (ME1)a | 34 ± 3.0 (16) | 32 ± 2.0 (6) | 38 ± 4.2 (8) |
| Aspartate aminotransferasea,b | 595 ± 32 (7) | 778 ± 116 (10) | 528 ± 32 (9) |
| NADP isocitrate dehydrogenasea,b | 208 ± 20 (12) | 235 ± 30 (6) | 198 ± 19 (10) |
| Glutamate dehydrogenasec | 96 ± 7.6 (8) | 129 ± 25 (6) | 99 ± 7.7 (10) |
| Malate dehydrogenasea,b | 7000 ± 800 (7) | 16,300 ± 3,300 (9) | 6900 ± 900 (8) |
| Pyruvate dehydrogenasec | 15.1 ± 1.7 (10) | 14.2 ± 1.3 (8) | 3.7 ± 0.2 (12) |
a Enzyme rates are expressed per mg of protein in the whole-cell homogenate supernatant fraction. Homogenate supernatant fractions were prepared so that mitochondria would be ruptured.
b Thus, in the case of isoforms of the three enzymes that are present in both the mitochondrial matrix and the cytosol, the values shown represent the sum of both activities.
c Enzyme rates are expressed per mg of protein of whole-cell homogenate protein.
d p is < 0.001 versus same assay rat islet and INS-1 832/13 cell values.