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Amino acid analyses of L-lactate dehydrogenase from baker's show that the minimum molecular weight (53 000 daltons) of the protein is much lower than found in the literature (80 000). This result, combined with those reported in the following papers, leads to a revision of the dimeric model generally accepted for cytochrome b2 [ABSTRACT FROM AUTHOR]

Amino acid analyses of L-lactate dehydrogenase from baker's show that the minimum molecular weight (53 000 daltons) of the protein is much lower than found in the literature (80 000). This result, combined with those reported in the following papers, leads to a revision of the dimeric model generally accepted for cytochrome b2 [ABSTRACT FROM AUTHOR]

An X-ray diffraction study has been performed by the powder technique on two crystalline forms of yeast cytochrome b2. Type II (DNA-free) cytochrome b2 crystallizes in the trigonal system, the parameters of the unit cell being a = 168.2 Å and c = 112.0 Å, whereas type I (DNA-containing) cytochrome b2 crystallizes in the tetragonal system with a = 99.1 Å and c = 87.0 Å. Measurement of the crystal density and of the partial specific volume of the protein (found to be 0.754 cm³ g at 25°) enables a precise determination of the molecular weight of cytochrome b2 to be obtained. In this respect, the values 234 6000 - 8000 and 235000 - 10000 were found for type II and type I crystals respectively. These results, although in complete concordance, are quite different from the previously accepted value (approx. 180000 from sedimentation studies based on v = 0.71 cm³ /g). Space-groups and protein contents of the crystals show that this protein is composed of at least two, or even four, identical protomers. [ABSTRACT FROM AUTHOR]

The specific activities expressed as µmol×g wet wt-1min-1 of D-triokinase and NADlinked glycerol dehydrogenase, with D-glyceraldehyde as substrate, were determined in the 27 500 × g supernatant fraction of livers from rats subjected to various dietary and hormonal programs. The specific activity of triokinase varied over a three-fold to four-fold range, being lowest in livers of diabetic rats fed a Purina Chow arid highest in livers of intact rats fed 72% fructose diets containing casein; total triokinase activity per liver was five-fold to six-fold greater in the latter group than in the former group. The specific activity of triokinase also increased in livers of rats fed diets of 72% glucose or 72% dextrin plus 18% casein. Fructose feeding caused a decrease in specific activity of glycerol dehydrogenase. Glucagon had no effect on the specific activity of either enzyme in livers of fasted rats. Cortisone tended to increase the specific activity of triokinase as well as its total activity in livers of rats fed the Purina Chow. After only 48 h of a 72% fructose-18% casein diet, liver weight was increased 50% relative to livers of rats fed the Purina Chow. Triokinase is subject to regulation in livers of adult male rats. The data indicate that the NAD-linked glycerol dehydrogenase is also subject to regulation but to a lesser extent. If glucagon does stimulate the flux of carbon in the triokinase or the NAD-linked glycerol dehydrogenase reactions, it is not as the result of increases iii enzyme concentrations as determined by assayable activity measurements. [ABSTRACT FROM AUTHOR]