Redox Enzymes in the Archaea
Edward J. Crane III, Charles S. Hummel and Evan T. Hal
from: Archaea: New Models for Prokaryotic Biology (Edited by: Paul Blum). Caister Academic Press, U.K. (2008)
One of the hallmarks of living systems is their ability to use favorable redox reactions in the conversion of energy to forms that are useful to the cell. Microbes in the kingdom archaea contain many unique redox enzymes, an observation which may result from the wide range of strategies they employ for energy conversion, the many extreme environments they inhabit, and the evolutionary separation of the archaea from bacteria that catalyze similar reactions. This chapter discusses archaeal redox enzymes, focusing mainly on enzymes that either 1) are unique to this kingdom, 2) appear to provide a selective advantage under extreme conditions, or 3) may be present outside the archaea but have been best characterized from archaeal sources. Subjects covered include enzymes involved in sulfur metabolism, including both sulfur oxidation and reduction and the hydrogenases frequently associated with sulfur reduction, as well as several enzymes involved in electron transport. The central metabolic pathways of many archaeons utilize unique enzymes, and these enzymes are also discussed, with a focus on tungsten and ferredoxin-dependent enzymes and small proteins that participate in electron transfer. Enzymes of archaeal anti-oxidant systems, including the superoxide reductase system of Pyrococcus are also covered, as are some enzymes from the uniquely archaeal methanogenesis pathway read more ...