Abstract: A pressure regulating device for a gas supply system of a gas turbine plant, having a pressure reduction unit for reducing the pressure of an inflowing gas, in particular a combustion gas, a compressor system for compressing the in-flowing gas and connected in parallel to the pressure reduction unit, and a regulating valve arranged on the output side of the pressure reduction unit, via which valve the pressure reduction unit can be fluidically separated on the output side from the compressor system. A gas supply system for a gas turbine plant has a corresponding pressure regulating device and a method for pressure regulation of a gas, uses a gas supply system with a corresponding pressure regulating device.