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Time- and dose-dependent measurements of metabolites of galactose (with glucose as control) in various organs of rats are discussed. Not only the liver but especially the brain and to a lesser extent the muscles also have the capacity to take up and metabolize galactose. Primarily, the concentrations of UDP-galactose, a pivotal compound in the metabolism of galactose, and UDP-glucose are measured. An important feature lies in the demonstration that galactose and glucose are metabolized to amino acids and that the only increases observed in the brain appear in the concentrations of glutamate, glutamine, GABA measured after acute galactose loads. In addition the increase in the amino acid concentrations after galactose has been administered persists for longer periods of time than after glucose administration. This conversion of hexoses, especially galactose, to amino acids requires the consumption of ammonia equivalents in the brain; this finding might stimulate the use of galactose as a new means of removal of this neurotoxic compound from the brain in patients suffering from hepatic encephalopathy or Alzheimer's disease.

The binding of fluoride ion (F-) and inorganic phosphate (Pi) to the yeast enolase-Mn complex was investigated by UV difference and proton relaxation rate (PRR) techniques. The F and the Pi ligands induce characteristic UV difference spectra of the E-Mn complex which were used to quantitate the binding of these ligands. The studies were performed in the presence of excess Mn2+ ([Mn2+]/[E], = 8.0). The Kd value for F was 0.6 f 0.2 M, and for Pi the Kd was 0.3 f 0.1 mM. The quaternary, E-Mn-F-Pi, complex also showed a UV difference spectrum. The Kd value for Ffrom the quaternary complex was < l o mM, and the Kd for Pi from the quaternary complex was 0.5 f 0.2 pM, demonstrating a strong positive cooperativity in ligand binding. In the PRR studies, lower ratios of Mn2+ to enzyme, which had some effect on both Pi binding to enolase-Mn and on Fbinding to enolase-Mn-Pi, were used. The binary enolase-Mn complex has an enhancement of 13-15. Titration of the binary complex with F gave a ternary enhancement of 7 and a Kd value of 0.6 f 0.1 M with either 0.7 or 3.0 Mn2+ per enolase dimer. Titration of the binary complex with Pi gave a ternary enhancement of 10 with a Kd of 1.2 f 0.2 mM and 0.6 f 0.1 mM with 0.64 and 2.5 Mn2+ per enolase dimer, respectively. E n o l a s e [phosphoenolpyruvate hydratase (EC 4.2.1.1 I)] is