Characterisation of hepatic microsomal glucose-6-phosphatase from broiler chickens.
1. The hepatic glucose-6-phosphatase (G-6-Pase) kinetic variables from chickens were studied in intact and disrupted microsomes using two substrates: glucose-6-phosphate (G-6-P) and pyrophosphate (PPi). They were studied from embryonic life to 51 d of age. 2. The phosphohydrolase activity studied in the broiler chicken liver microsomes corresponds to a true glucose-6-phosphatase. 3. The enzyme VMAX with both substrates in intact and disrupted microsomes showed 2 maxima: one in 19-d-old embryos and the other in 9-d-old chickens. Pyrophosphatase (PPase) VMAX in intact microsomes was higher than that of the G-6-Pase at all ages studied, except in 12 d embryos and 3-d-old chicks. In disrupted microsomes the VMAX of both enzymatic activities were similar. The G-6-Pase latency was high in the 19-d-old embryos and 51-d-old chickens. 4. The KM for PPi and G-6-Pase decreased when microsomes were disrupted. In intact microsomes the G-6-P KM was low in embryos and 3-d-old chicks and later increased. On the other hand, the PPi KM in intact microsomes showed little change during the animal's life and was lower than that of G-6-P. In disrupted microsomes the KM for both substrates were similar. 5. These results suggest a sequential incorporation of the G-6-Pase system components in the endoplasmic reticulum.
Gonzalez-Mujica
F
F
Sección de Bioquímica Médica, Instituto de Medicina Experimental, Facultad de Medicina, Universidad Central de Venezuela, Apartado postal 50587, Sabana Grande, Caracas, Venezuela. gonzalef@latinmail.com
Motta
N
N
Márquez
A H
AH
D000375:Aging; D000818:Animals; D002642:Chick Embryo / Q000378:metabolism*; D002645:Chickens / Q000378:metabolism*; D011756:Diphosphates / Q000493:pharmacokinetics*; D005952:Glucose-6-Phosphatase / Q000493:pharmacokinetics*; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D010101:Oxygen Consumption; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism
D011756:Diphosphates; D010744:Phosphoric Monoester Hydrolases; D005952:Glucose-6-Phosphatase