Adenylate cyclase (AC) is the key enzyme that catalyzes the formation of cAMP from ATP. In this study

we discovered two novel class III ACs with a halophilic property from

Thermobifida halotolerans

DSM 44931 (ThAC) and

Haloactinopolyspora alba

DSM 45211 (HaAC)

respectively. The recombinant ThAC and HaAC were expressed in

Escherichia coli

with molecular weights of 36.1 and 36.0 kDa respectively. The presence of 2500 and 2200 mmol·L

-1

NaCl significantly enhanced the enzyme activities of ThAC and HaAC

with 22-fold and 7.4-fold higher activities compared to those without NaCl

respectively. Several divalent metal ions were found to activate the recombinant ACs to different extents

and the optimal metal ion was Mg

2+

for both ThAC and HaAC with concentrations of 80 mmol·L

-1

and 40 mmol·L

-1

respectively. Purified ThAC and HaAC had the optimal specific activities ((4.59 ±0.35)×10

4

and (7.76 ±0.52)×10

4

U·mg

-1

) and catalytic efficiency (4.47 and 5.30 L·mmol

-1

·s

-1

) at 45 ℃ and 40 ℃ respectively

while the optimum pH of both two recombinant ACs was 10.0. This is the first report of

the halophilic Class III ACs

which could make new contributions to explore and study ACs for further associated investigations.