Serological evidence for H-Y antigen in XO-female mice.

H-Y antigen was examined in XX-, XY-, and XO- mice using spleen, kidney, and liver cells of the animals for the absorption of the anti-H-Y antiserum produced in the rat. The cells of the XY- and XO-mice were found to be H-Y antigen-positive while the cells of the XX-mice were negative. As in Turner syndrome patients with 45,X, in the XO-female mice the H-Y antigen titre was reduced as compared to normal XY-male mice; intermediate values between those of normal male and female mice were obtained. These results clearly indicate that as in man, in the mouse the structural gene for H-Y antigen is not Y-linked but is located on an autosome. Furthermore, the concept of the regulation of the H-Y antigen gene expression in the human (Wolf et al. 1980a, b) by an X-linked repressor gene, escaping X-inactivation in the XX-female and an Y-linked inducer gene also seems to hold true in the mouse.

Separation and characterization of two inorganic pyrophosphatases from spinach leaves.

Two inorganic pyrophosphatases (pyrophosphate phosphohydrolase, E.C.3.6.1.1) have been identified in spinach (Spinacia oleracea L.) leaves. The two isoenzymes were readily separated by polyacrylamide gel electrophoresis and by isoelectric focusing between pH 4 and 6. One isoenzyme is located in the chloroplasts whereas the other form was isolated from the soluble "cytoplasmic" fraction. In addition, a third form appeared when the isolation procedure started from a crude extract from whole leaves. It is suggested that this form represents an aggregation between the two natural species.The three forms differ in their kinetic properties, such as substrate affinity and pH optima. The apparent K m values were determined to be 10(-5)M for the chloroplastic isoenzyme, 7×10(-5) M for the "cytoplasmic" isoenzyme and 3×10(-5) M for the third form. At limiting Mg(2+) concentrations, the corresponding pH optima were found to be 8.55, 8.95 and 8.75, respectively.

[The influence of starch on the activity of pyrophosphatase from isolated spinach chloroplasts]. / Der Einfluß von Stärke auf die Aktivität der Pyrophosphatase aus isolierten Chloroplasten.

The activity of the inorganic pyrophosphatase from isolated spinach (Spinacia oleracea L.) chloroplasts is strongly dependent upon the addition of magnesium ions. Since the complex of the bivalent ion with inorganic pyrophosphate is the real substrate, a definite Mg(2+)/Na4P2O7-ratio is required for maximum activity. When the activity was measured in particle-free extracts from chloroplasts, this ratio was shown to be approximately 3. However, an increase up to 10 was observed in the presence of thylakoid membranes. Furthermore, the kinetics in the presence of broken chloroplasts becomes sigmoidal.The altered kinetics have been shown to be due to starch located in the thylakoids. The inhibitory effect is caused by amylose alone but not by amylopectin., Detailed kinetic analysis of the inhibition showed no influence of amylose on the Hill-coefficient. Since ethylenediaminetetracetic acid was shown to have similar effects as amylose, starch might regulate the pyrophosphatase activity by binding Mg(2+)-ions.

Catalytic properties and regulatory diversity of inorganic pyrophosphatases from photosynthetic bacteria.

Soluble inorganic pyrophosphatases of five species of nonsulfur purple bacteria were investigated in respect to reaction kinetics, regulatory behavior, and other characteristics. The enzymes appear to fall into two groups with correlated properties. The pyrophosphatases of Rhodopseudomonas capsulata and R. spheroides have molecular weights of approximately 60,000, are stabilized by Co(2+), and exhibit simple Michaelis-Menten reaction kinetics. On the other hand, the enzymes of R. palustris, R. gelatinosa, and Rhodospirillum rubrum are larger (molecular weight approximately 100,000), require Zn(2+) for maintenance of catalytic activity, and show complex reaction kinetics; these pyrophosphatases are activated by free Mg(2+) ions and, in the absence of the latter, are inhibited by 2-phosphoglyceric acid. The results described indicate the existence of alternative control patterns for regulation of intracellular turnover of phosphate, which is in part mediated by pyrophosphatases.