Preparation and properties of yeast aldolase.

Aldolases derived from various sources may be differentiated into two types according to whether or not they are inhibited by metal-chelating agents (2). Warburg and Christian (3) first recognized a distinctive difference in the properties of yeast and muscle aldolase. The yeast enzyme was strongly inhibited by cyanide, pyrophosphate, cysteine, and cr ,cr’-dipyrridyl, and the inhibition was reversed by divalent metal ions (Zn”, FeII, CoIi, Cu”). A dissociable metal ion activator (probably Fe”) for the yeast enzyme was therefore proposed. It was later reported that the highly purified preparations of Warburg and Gawehn (4) contained considerable quantities of zinc and only traces of iron (5). The inhibition of the yeast enzyme by metal-chelating agents thus was correlated with the presence of zinc in the protein. In contrast to the yeast enzyme, muscle aldolase was not affected by the presence of metal-chelating agents (3), and did not contain significant quantities of any divalent ion (3, 5). In line with the above, muscle aldolase is considered the prototype of the metal ion-independent (type I), and similarly, yeast aldolase is the prototype of the metal ion-dependent (type II) aldolases. In addition to the muscle enzyme (studied in the rat and rabbit), the bovine liver enzyme is appropriately classified as a type I aldolase since it is not inhibited by chelating agents, and does not contain divalent ions (6). The aldolase from peas (7) also may be placed tentatively in this category. In contrast, most aldolases which have been studied in microbiological systems are apparently type II aldolases. For example, the activity of the aldolase from several Aspergillus species is inhibited by chelating agents, and the inhibition is reversed by ZeI’, Fe”, Co” and Mn”; moreover, a highly purified preparation of the enzyme from Aspergillus niger contains 1 mole of Zn per 50,000 g of protein (8). The aldolase activity in aged extracts of Clostridium perfringens is stimulated markedly by Fe?’ or CoII, together with cysteine (9) ; therefore, in this instance, the metal ion appears freely dissociable. The available evidence suggests that other microbial systems contain type II aldolases (e.g. Escherichia co& (10) Lactobacillus bijidus (ll), Brucella s&s (12)) and Mycobacterium tuberculosis (13).