Histidine Carboxylase of Leuconostoc-Oenos-9204 - Purification, Kinetic-Properties, Cloning and Nucleotide- Sequence of the Hdc Gene

COTON, E; ROLLAN, GC; LONVAUD FUNEL, A

JOURNAL OF APPLIED MICROBIOLOGY

Blackwell Publishing

Año: 1998 vol. 84 p. 143 - 151

Histidine decarboxylase (HDC) was purified to homogeneity from Leuconostoc ’ nos 9204, a wine lactic acid bacterium. Histidine decarboxylase comprised two subunits, respectively á and â. The hdc gene was cloned and sequenced. The gene encodes a single polypeptide of 315 amino acids, demonstrating that Leuc. oenos nos 9204 HDC was synthesized as a precursor proHDC ð6 (Mr 205 000). A cleavage between Ser-81 and Ser-82 generated the á (Mr 25 380) and â (Mr 8840) chains, which suggested that the holoenzyme exists as a hexameric structure (áâ)6. At the optimal pH of 4·8, the HDC activity exhibited a simple Michaelis-Menten kinetic (Km = 0·33 mmol l−1, Vmax = 17·8 ìmol CO2 min−1 mg−1), while at pH 7·6 it was sigmoidal (cooperativity index of 2). Histamine acted as a competitive inhibitor (Ki = 32 mmol l−1). The similarities of these results with those described for other bacterial HDC support the assumption that the pyruvoyl enzymes evolved from a common ancestral protein and have similar catalytic mechanisms. These results also confirmed that the main lactic acid bacterial species responsible for malolactic fermentation in red wine is able to produce histamine. Bacteria carrying the HDC activity must be avoided during selection of strains for the production of malolactic starters.