( 4 ) 1 U is the amount of enzyme which makes 1 microgram of azo-casein soluble in trichloracetic acid per minute at pH 7,5 and 37 °C.
4 1 U je količina encima, ki naredi 1 mikrogram azo-kazeina topnega v trikloracetni kislini na minuto pri pH 7,5 in 37°C.