Structural and functional characterisation of a cold-active yet heat-tolerant dehydroquinase from Glaciozyma antarctica PI12

Dehydroquinase or 3-dehydroquinate dehydratase (DHQD) reversibly cleaves 3-dehydroquinate to form 3-dehydroshikimate. Here, we describe the functional and structural features of a cold active type II 3-dehydroquinate dehydratase from the psychrophilic yeast, Glaciozyma antarctica PI12 (GaDHQD). Functional studies showed that the enzyme was active at low temperatures (10-30.C), but displayed maximal activity at 40 degrees C. Yet the enzyme was stable over a wide range of temperatures (10-70 degrees C) and between pH 6.0-10.0 with an optimum pH of 8.0. Interestingly, the enzyme was highly thermo-tolerant, denaturing only at approximately 84 degrees C. Three-dimensional structure analyses showed that the G. antarctica dehydroquinase (GaDHQD) possesses psychrophilic features in comparison with its mesophilic and thermophilic counterparts such as higher numbers of non-polar residues on the surface, lower numbers of arginine and higher numbers of glycine-residues with lower numbers of hydrophobic interactions. On the other hand, GaDHQD shares some traits (i.e. total number of hydrogen bonds, number of proline residues and overall folding) with its mesophilic and thermophilic counterparts. Combined, these features contribute synergistically towards the enzyme's ability to function at both low and high temperatures.

Automated summary

The study describes a type II 3-dehydroquinate dehydratase from the cold-adapted yeast Glaciozyma antarctica PI12, which is active at low temperatures with maximal activity at 40 degrees C, displaying stability and high thermo-tolerance, denaturing only at approximately 84 degrees C. The enzyme possesses psychrophilic features compared to its mesophilic and thermophilic counterparts, contributing towards its ability to function at both low and high temperatures.