Xanthohumol is a yellow leaf pigment, present in all hop varieties. I t is a chalkone and isomerizes into a flavanone on alkaline treatment. Xanthohumol has the molecular formula C,,H ,,O ,, contains three active hydrogen atoms, one methoxylgroup, one carbonylgroup and two double bonds. Alkaline hydrolysis of xanthohumol yields p.oxybenzaldehyde, acetic acid arid methoxy-isoprenylphloroglucinol. Xanthohumol is represented by structure IV. (I4) S. M. Mc ELVAIN, The characterization of organic compounds. MacMillan Co New-York, p. 200 (1947).
Chicken egg yolk contains an adenosine deaminase that was investigated after purifying about 500 times. It has a pH optimum at 6.5, a K , of 6.6 x lo-' mol/l and an approximate molecular weight of 14000; higher molecular forms could not be detected. It was compared with the adenosine deaminases of chicken liver and blood plasma. From this comparison it is evident that this protein has undergone certain changes during the successive events leading to its final structure (secretion by the liver, transport through blood plasma to the oocytes and development of the egg) : a common subunit with an approximate molecular weight of 15 000 may be the basis of the physiological diversifications. Substrate specificity of the purified extracts extends to cytidine and guanosine also, although certain observations point to different enzymes being involved. Deoxyadenosine is also deaminated. Cu2+, Zn2+ and Pb2+ are inhibiting and free-SH seems essential for activity.
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