Effect of mycoplasma infection on pyruvate dehydrogenase complex activity of normal and pyruvate dehydrogenase complex-deficient fibroblasts

The fermentative mycoplasmas A. laidlawii JS, M. hyorhinis DBS-50, M. hyorhinis GDL and M. pneumoniae FH have very high apparent activities of pyruvate dehydrogenase (PDH) (EC 1.2.4.1) and pyruvate dehydrogenase complex (PDHC). Infection of normal and PDHC-deficient fibroblasts with these mycoplasma species resulted in a marked increase of the specific activity of these two enzymes, and under certain conditions could conceal the enzymatic defect. The non-fermentative mycoplasmas M. salivarium VV and M. arthritidis PG-6 have very low apparent activities of these two enzymes. Normal fibroblasts infected with non-fermentative mycoplasmas could appear as deficient in these two enzymes. The degree of interference depends on the number of mycoplasmas associated with the harvested cells. Besides the mycoplasma species, this depends (1) on the duration of infection which determines mycoplasmal titers and also can have a killing effect on both host cells and/or mycoplasmas; (2) harvest of the cells by scraping or trypsinization; (3) centrifugal force used in the collection of the cells; (4) washing and the inherent mechanical treatment; and (5) other possibilities.