Isolation, characterization, and physiological role of the pyruvate dehydrogenase complex and alpha-acetolactate synthase of Lactococcus lactis subsp. lactis bv. diacetylactis.
The pyruvate dehydrogenase complex of Lactococcus lactis subsp. lactis bv. diacetylactis has a specific activity of 6.6 U/mg and a Km of 1 mM for pyruvate. The specific activities of E2 and E3 in the complex are 30 and 0.36 U/mg, respectively. The complex is very sensitive to NADH inhibition and consists of four subunits: E1 alpha (44 kDa), E1 beta (35 kDa), E2 (73 kDa), and E3 (60 kDa). The L. lactis alpha-acetolactate synthase has a specific activity of 103 U/mg and a Km of 50 mM for pyruvate. Thiamine pyrophosphate (Km = 3.2 microM) and divalent cations are essential for activity. The native enzyme measures 172 kDa and consists of 62-kDa monomers. The role of both enzymes in product formation is discussed in view of NADH inhibition and competition for pyruvate.
Snoep
J L
JL
Department of Microbiology, University of Amsterdam, The Netherlands.
Teixeira de Mattos
M J
MJ
Starrenburg
M J
MJ
Hugenholtz
J
J
D000095:Acetolactate Synthase / Q000302:isolation & purification / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D013294:Lactococcus lactis / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D011768:Pyruvate Dehydrogenase Complex / Q000302:isolation & purification / Q000378:metabolism*; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid; D013835:Thiamine Pyrophosphate / Q000378:metabolism
D002413:Cations, Divalent; D011768:Pyruvate Dehydrogenase Complex; D011773:Pyruvates; D009243:NAD; D019289:Pyruvic Acid; D000095:Acetolactate Synthase; D013835:Thiamine Pyrophosphate