Studies of enzyme action. XV.—Urease: a selective enzyme

Abstract

The production of urea from the metameric ammonic cyanate by Wöhler, in 1828, was naturally regarded as an achievement of great importance in view of the part of the substance plays in the human economy—very nearly the whole of the nitrogen secreted being voided as urea; the synthesis of such a copound was a severe blow to the vitalistic conceptions which had been dominant in organic chemistry and justly excited attention, as it broke down the barriers up to that time held to be existent between the organic and inorganic world. The attributes of urea are in many ways remarkable and scarcely in correspondence with the simple formula ordinarily assigned to it. It is generally spoken of in the text-books as carbamide but its properties are more nearly those of the isomeric hydroxy-amino-imino - derivative: an explanation may be found in the assumption that the two isodynamic substances are present in an aqueous solution in oscillatory equilibrium:— CO { NH 2 ⇌ C { NH NH 2 NH 2 . OH But it is probable that these two compounds, in turn, are in equilibrium with the hydrate common to both, C(NH 2 ) 2 (OH) 2 : as chemical changes are all reciprocal effects, the behaviour of urea is therefore subject to considerable variation and depends on the conditions under which it is placed; on this account, a name which is significant of the origin of the substance rather than of its functions is specially appropriate.