Catalytic subunit of the DNA primase complex and component of the DNA polymerase alpha complex (also known as the alpha DNA polymerase-primase complex - primosome/replisome) which play an essential role in the initiation of DNA synthesis (PubMed:8918794). The primase subunit of the polymerase alpha complex initiates DNA synthesis by oligomerising short RNA primers on both leading and lagging strands (PubMed:8918794). ssDNA + n dNTP = ssDNA/pppdN(pdN)n-1 hybrid + (n-1) diphosphate. The presence of the regulatory subunit accelerates the kinetics of initiation and primer extension. Optimum pH is 7.6. Heterodimer of a catalytic subunit and a regulatory subunit, also known as the DNA primase complex. The bound zinc ion is not a cofactor. It is bound to a zinc knuckle motif that may be involved in sequence recognition and the binding of ssDNA (By similarity). Belongs to the eukaryotic-type primase small subunit family.