title: The glucose-6-phosphatase system in the retina.
abstract: The retinal glucose-6-phosphatase system was studied in rabbits. Following subcellular fractionation of the retina by differential centrifugation, the microsomal fraction was used for spectrophotometrical assay of the phosphate release. Assays were performed with intact and Triton X-100-treated preparations. Intactness of the microsomal preparations was assessed by using 2 mM mannose-6-phosphate as a substrate. Latencies towards glucose-6-phosphate and mannose-6-phosphate were 13.1 +/- 4.1% (n = 5) and 92.5 +/- 2.8% (n = 5) respectively; the difference between them was significant (P < 0.001). Pyridoxal-5'-phosphate specifically inhibited the retinal glucose-6-phosphate translocase activity at concentrations of 5-10 mM. Postnatal development was studied at postnatal days 1, 10, 17, 25, 36, 46, 54 and 70. At the postnatal 17th day, the retinal glucose-6-phosphatase specific activity was 60.1 +/- 3.8 (n = 3) nmol/min/mg protein which was one-third of the adult level [173.6 +/- 26.2 (n = 6) nmol/min/mg protein] (P < 0.001). This finding suggested that, in the rabbit, development of this enzyme system might coincide with development of retinal glucose catabolism.
authors.affiliation: Department of Ophthalmology, Tohoku University School of Medicine, Miyagi, Japan.
authors.forename: Y K
authors.initials: YK
authors.lastname: Durlu
authors.forename: S
authors.initials: S
authors.lastname: Ishiguro
authors.forename: M
authors.initials: M
authors.lastname: Tamai
mesh_terms: D000818:Animals; D004795:Enzyme Stability; D005260:Female; D005952:Glucose-6-Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008297:Male; D008360:Mannosephosphates / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D011817:Rabbits; D012160:Retina / Q000201:enzymology* / Q000254:growth & development; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D005958:Glucosephosphates; D008360:Mannosephosphates; C027693:mannose-6-phosphate; D019298:Glucose-6-Phosphate; D011732:Pyridoxal Phosphate; D005952:Glucose-6-Phosphatase