Portal de Periódicos da CAPES

Investigations on phosphofructokinase (PFK, EC 2.7.1.11) in bovine lenses in dependence on age, topographic distribution and water soluble protein fractions

1977; Elsevier BV; Volume: 24; Issue: 4 Linguagem: Inglês

10.1016/0014-4835(77)90151-8

1096-0007

F. Bous, O. Hockwin, Christian Ohrloff, J. Bours,

Aldose Reductase and Taurine

The specific activity of phosphofructokinase and its affinity to the substrate fructose-6-phosphate was determined with reference to the age of lens. The allosteric behaviour of the enzyme was eliminated by choosing the appropriate assay conditions. Age-dependent changes could be observed in both parameters. The specific activity decreased by 50% during the first 4 years, thereafter remaining almost constant. It was highest in the lens equator followed by anterior and posterior cortical region and lens nucleus. The substrate saturation curve for the calf lens shows a typical hyperbolic course, (Michaelis-Menten) and the slope of Lineweaver-Burk plot gives a Km-value of 5 × 10−5 m for F-6-P. For the nucleus of calf and bovine lenses the Lineweaver-Burk diagram shows convex curves indicating heterogeneity of the kinetic properties due to aging. After separation of the water soluble proteins the activity of phosphofructokinase could be localized in the α-crystallin as well as in the β-crystallin fraction.