Functional residues on the enzyme active site of glyoxalase I from bovine brain.

Bovine brain glyoxalase I was investigated in order to identify amino acid residues essential for its catalytic activity. This enzyme is a 44-kDa dimeric protein which exhibits a characteristic intrinsic fluorescence, with an emission peak centered at 342 nm. The total of eight tryptophan residues/molecule was estimated by using a fluorescence titration method.

Purification and partial characterization of glyoxalase I from bovine brain.

Glyoxalase I was purified to homogeneity from bovine brain using affinity chromatography on S-hexylglutathione-Sepharose 6B with a yield of 22%. The enzyme was a dimer (44,000 Daltons) composed of, apparently, identical subunits (22,000 Daltons), as shown by SDS electrophoresis, and contained one mole of Zn2+/monomer. The active site metal ion, Zn2+, was removed by dialysis against EDTA, but the activity of the apoenzyme obtained was not completely restored after addition of Co2+ and Zn2+ (<25%), while a recovery of 50% was obtained after addition of Mg2+.

Inhibition studies on membrane adenosine deaminase from human placenta.

The ecto form of adenosine deaminase isolated from human placental membrane was tested towards its sensitivity against adenosine deaminase inhibitors, such as aza and deaza analogues of adenosine and erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA). Ki values of the inhibitors observed were similar to these obtained for the small form of adenosine deaminase purified from human erythrocytes, indicating that the presence of the binding protein on placental adenosine deaminase does not produce alteration in the binding of these inhibitors on the enzyme active site. The inhibition rate of 2'-deoxycoformycin, one of the most potent ADA inhibitors is affected by the presence of the binding protein on human placental adenosine deaminase, that probably modulates the rearrangement of the active site produced by the binding with this tight-binding inhibitor.

Functional residues at the active site of bovine brain adenosine deaminase.

Brain adenosine deaminase was investigated in order to identify amino acid residues essential for its catalytic activity. The pH dependence of log Vmax shows that the enzyme activity depends on two ionizing groups with pK values of 5.4, that must be unprotonated, and 8.

Glycosylation of RNA polymerase II from wheat germ.

RNA polymerase II from wheat germ was analyzed for the presence of sugars. The two largest subunits and the 27 and 25 kDa subunits were found to be glycosylated by a variety of sugars. However, no N-acetylglucosamine was detected, which was found by Kelly et al.