A couple of points, concerning two other Soviet 45mm AA guns:
The standard Soviet medium calibre naval AA gun of WW2 and for a while thereafter was in 45mm calibre, but was a manually-loaded single-shot gun. The ammunition was based on that of the Army's 45mm tank/anti-tank gun.
Just before WW2 the Soviet Army very nearly adopted a Bofors-derived automatic 45mm AA gun, before rejecting it in favour of the 37mm because they felt it was too big and heavy.
There were of course links between the German and Soviet militaries before WW2, including equipment exchanges, so it may be difficult to work out the exact sequence of development.