Preliminary crystallographic data for the thiamin diphosphate-dependent enzyme pyruvate decarboxylase from brewers' yeast

Single crystals of the thiamin diphosphate (the vitamin B₁ coenzyme)-dependent enzyme pyruvate decarboxylase (EC 4.1.1.1) from brewers' yeast have been grown using polyethylene glycol as a precipitating agent. Crystals of the homotetrameric version α₄ of the holoenzyme are triclinic, space group P1, with cell constants a = 81.0, b = 82.4, c = 116.6 Å, α = 69.5, β = 72.6, γ = 62.4°. The crystals are reasonably stable in a rotating anode x-ray beam and diffract to at least 2.5 Å resolution. The V(m) value of 2.55 Å/dalton is consistent with a unit cell containing four subunits with mass of approximately 60 kDa each. Rotation function results with native data indicate strong noncrystallographic 222 symmetry relating the four identical subunits, thus density averaging methods are likely to play a role in the structure determination.