Microbial Mythology

Textbooks and web sites propagate various misconceptions and simple errors about microbiology. Here we provide a place for microbiology educators to set the record straight. Authors: Please provide primary reference, in open-access sources whenever possible.

TCA Cycle: ATP or GTP?

Succinyl-CoA synthetase, also known as succinate thiokinase, is the enzyme of the TCA cycle that interconverts succinyl-CoA with succinate, coupled to formation of a nucleotide triphosphate. Many textbooks and web sites state that succinyl-CoA synthetase phosphorylates only GDP to GTP. See example.
According to the primary literature, however, ADP phosphorylation predominates in E. coli (Margaret Birney et al, 1996) whereas in Pseudomonas sp., various nucleotide diphosphates are phosphorylated (Vinayak Kapatral et al, 2000). Human mitochondria have two forms of the enzyme, which phosphorylate ATP and GTP respectively (David Lambeth et al, 2004).