Characterisation of an intermediate in neurophysin biosynthesis in the guinea pig

In addition to oxytocin (OT), vasopressin (AVP) and their respective neurophysins (NPs), another [35S]cysteine incorporating component is present in the guinea pig neurohypophysis. Gel filtration and Con A affinity chromatography revealed that this component was larger than NP and was glycosylated. NP-immunoreactivity was assessed using antisera which distinguish the OT- and AVP-related NPs. Whilst the anti-NP antiserum detected only one component (guinea pig NP), the anti-NP antiserum detected both NP and the glycosylated 35S-labelled component. These results suggest that a significant amount of NP in guinea pig neural lobes bears a glycopeptide extension and represents a partially processed form of the AVP precursor in this species.