Transport of iron by mycobactin in

The uptake of ⁵⁵FeCl₃ and ⁵⁵Fe-mycobactin has been followed. FeCl₃ was the more effective source of iron for the cell although Fe-mycobactin was adsorbed on to the cell very quickly. The mycobactin within the cell is the prime receptor for Fe³⁺ and it probably functions as an ionophore for the transport of iron across the lipid envelope of the cell. Release of iron from mycobactin occurs by a NADH-dependent reductase forming Fe²⁺ and conditions for observing the activity of this unique enzyme are given.     

Interaction of guanosine 5′-diphosphate, 2′-(or 3′-) diphosphate(ppGpp) with elongation factors from

The interactions of guanosine 5′-diphosphate, 2′-(or 3′-) diphosphate(ppGpp) with the polypeptide elongation factors Tu(EF Tu) and G(EF G) have been studied. The data indicate that ppGpp binds with EF Tu to form an EF Tu-ppGpp complex, and inhibits, in a competitive manner, the exchange reaction of Tu-GDP and ³H-GDP. The ribosome-dependent GTPase reaction catalyzed by EF G is also depressed by ppGpp.     

Fucoxanthin metabolites in egg yolks of laying hens

Feeding experiments were conducted with White leghorn laying hens fed a carotenoid depleted control diet (containing some zeaxanthin and lutein) or this diet supplemented with 15% seaweed meal of established carotenoid composition. Egg yolk colour was estimated by use of a Roche Yolk Colour Fan and by detailed quantitative and qualitative carotenoid analysis of individual eggs of three laying hens during 4 weeks. Identification of the carotenoids included HPLC, VIS, MS, ¹H NMR data and partial synthesis. The results confirmed that fucoxanthin, the major carotenoid in seaweed meal, is not transferred to the yolk. However, fucoxanthin gave rise to the metabolites fucoxanthinol, fucoxanthinol 3'-sulphate and paracentrone, that are ascribed to enzymatic modifications occurring in the hens. The difuranoid auroxanthin encountered in the egg yolk was ascribed to violaxanthin and/or its furanoid derivatives present in the seaweed meal. Colour of individual yolks varied considerably. The pigmentation level is discussed.