Assimilatory Sulfate Reduction

Abstract

The roles of sulfur and nitrogen in cell nutrition show many similarities. Both must be reduced by living systems to form proteins and other macromolecules and both, therefore, appear among the macroelements required by plants and plant-like microorganisms. Nutritional interactions between the two elements have been described (Friedrich and Schrader, 1978) and both elements show a rather uniform distribution throughout the tissues and Organs of higher plants and among cells of microorganisms. Sulfate reduction occurs in mitochondria and microbodies in Euglena cells (Brunold and Schiff, 1976) and is localized in the plastids of higher plants (Schmidt and Schwerin, 1971; Schwenn and Trebst, 1976). Since cell, tissue, and organ cultures can be grown on sulfateasasolesulfursource (White, 1963; White and Grove, 1965;Butenko, 1968; Thomas and Davey, 1975), and since nongreen tissues such as beet discs (Ellis, 1963) and roots (Pate, 1965) reduce sulfate, assimilatory sulfate reduction must be widely distributed throughout the plant; studies of the localization of certain enzymes of sulfate reduction are in agreement (Mayer, 1967; Ellis, 1969; Onajobi et al., 1973; Schmidt, 1976; Tamura et al., 1976; Cacco et al., 1977; Fankhauser and Brunold, 1978, 1979). In this paper we will try to summarize what is known of the process of assimilatory sulfate reduction and how it might have evolved; some recent work on an enzymatic reaction of adenosine 5′ phosphosulfate (APS) and ammonia (Fankhauser et al., 1979; Fankhauser and Schiff, 1980; Fankhauser et al., 1980) will also be described which may provide a connection between sulfur and nitrogen metabolism.