Catalyzes the reaction of cyanate with bicarbonate to produce ammonia and carbon dioxide. cyanate + 3 H(+) + hydrogencarbonate = 2 CO2 + NH4(+) Optimum pH is 7.6. Thermostable for 1 hour up to 60 degrees Celsius. Induced by cyanate and down-regulated by arginine. Belongs to the cyanase family.