The ornithine aminotransferase (OAT) activity of mouse was found to be highest in the small intestine. The mitochondrial OAT from mouse small intestine was purified to homogeneity by the procedures including heart treatment, ammonium sulfate fractionation, octyl-Sepharose chromatography, and Sephadex G-150 gel filtration. Comparing to the amino acid sequence of mouse hepatic OAT, six N-terminal amino acid residues have been deleted in intestinal OAT. However, the subsequent sequence was identical with that of hepatic OAT. The molecular weights of both intestinal and hepatic OAT were estimated as 46 kDa by SDS-gel electrophoresis and as 92 kDa by gel filtration, indicating that both native OATs are dimeric. Biochemical properties of intestinal OAT, such as molecular weight, pH optimum and K(m) values for L-ornithine and alpha-ketoglutarate, were similar to those of hepatic OAT. However, intestinal OAT was more labile than hepatic OAT to tryptic digestion.
Amino Acid Sequence ; Animal ; Intestine, Small/enzymology* ; Liver/enzymology ; Male ; Mice ; Mice, Inbred ICR ; Molecular Sequence Data ; Molecular Weight ; Ornithine-Oxo-Acid Transaminase/metabolism* ; Ornithine-Oxo-Acid Transaminase/isolation & purification ; Ornithine-Oxo-Acid Transaminase/genetics* ; Tissue Distribution ; Trypsi

A pair of 19-year-old female identical twins was referred to our hospital with progressive visual loss. They exhibited bilateral chorioretinal atrophy involving the midperiphery on fundoscopy and fluorescein angiography. Bilateral visual field constriction was noted on dynamic Goldmann perimetry, and a markedly impaired response was observed on both photopic and scotopic electroretinograms. Cystoid macular edema was identified in both eyes on optical coherence tomography. Plasma levels of ornithine were elevated. Based on these observations, the patients were diagnosed with gyrate atrophy of the choroid and retina. The clinical diagnosis was confirmed by mutation analysis of the ornithine-delta-aminotransferase (OAT) gene. Patients were treated with a pyridoxine supplement (300 mg/day) and an arginine-restricted diet to lower plasma levels of ornithine, which were successfully reduced without progression of chorioretinal atrophy for 15 months. Our report describes the first case of gyrate atrophy in the Korean population diagnosed by OAT gene analysis and treated with vitamin B6 dietary supplementation.
DNA/*analysis ; DNA Mutational Analysis ; Diagnosis, Differential ; Electroretinography ; Female ; Fluorescein Angiography ; Fundus Oculi ; Gyrate Atrophy/*diagnosis/enzymology/genetics ; Humans ; *Mutation ; Ornithine-Oxo-Acid Transaminase/*genetics/metabolism ; Tomography, Optical Coherence ; Visual Acuity ; Young Adult