Table I.
Galactosyl Transferase Enrichment and Endosomal Contamination of Hepatic Golgi Fractions
| Golgi fraction | GalT (RSA) | NAGT | Endosomal contamination (125I-insulin) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| WNG | 160 ± 31 | (10) | 149 ± 45 | (3) | 9 ± 6 | (3) | ||||||
| GE | 74 ± 8 | (3) | 110 ± 18 | (2) | 38 ± 11 | (3) | ||||||
| Gi | 93 ± 31 | (3) | 120 ± 5 | (2) | 158 ± 44 | (3) | ||||||
The specific activity of UDP galactose ovomucoid galactosyl transferase (GalT) activity of the WNG fraction was 12.1 ± 0.2 nmols (SD) gal incorporated/min per mg cell fraction protein (n = 10). For UDP N-acetyl glucosamine ovalbumin N-acetyl glucosaminyl transferase (NAGT), the specific activity of the WNG fraction was 0.64 ± 0.15 nmols (SD) GlcNAc incorporated/min per mg cell fraction protein (n = 3). RSA (relative specific activity) is the enrichment activity of the fraction over the homogenate expressed as the mean ± SD or one-half variation. Endosomal contamination was evaluated by the 125I-insulin content of the Golgi fractions isolated from rats killed at 5 min after the intraportal vein injection of 125I-insulin (80 × 106 cpm, 1 μg) and is expressed as a function of the concentration of 125I-insulin in homogenates as fold enrichment in radioactivity over the concentration of 125I-insulin in the parent homogenates (mean ± SD). The number of separate experiments is indicated in parentheses.