FIG. 1.

Proposed citric acid cycle and related enzyme reactions in P. islandicum. The enzymes are as follows: 1, citrate synthase; 2, aconitate hydratase; 3, isocitrate dehydrogenase; 4, 2-oxoglutarate synthase; 5, succinate:CoA ligase (ADP forming); 6, succinate dehydrogenase; 7, fumarate hydratase; 8, malate dehydrogenase; 9, citrate lyase; 10, ATP citrate synthase; 11, acetate:CoA ligase (ADP forming); 12, acetate:CoA ligase (AMP forming); 13, pyruvate synthase; 14, pyruvate-water dikinase; 15, phosphoenolpyruvate carboxylase; 16, malate dehydrogenase (decarboxylating); 17, malate synthase; and 18, isocitrate lyase. Fd, electron carrier ferredoxin; FAD, flavin adenine dinucleotide; FADH₂, reduced flavin adenine dinucleotide.