Involvement of thymosin β4 and endoproteinase Asp‐N in the biosynthesis of the tetrapeptide AcSerAspLysPro a regulator of the hematopoietic system

Abstract

It is shown that AcSDKP a new regulator of the hematopoietic system can he generated from thymosin β₄ by a one‐step enzymatic cleavage in vitro and in vivo. AcSDKP and Tβ₄ were both detected in bone marrow cells (BMC'). Incubation of [³H]Tβ₄ with either intact or lysed BMC led to the formation of [³H]AcSDKP whereas the labelled tetrapeptide was not degraded under these conditions. Model enzymatic degradation of Tβ₄ carried out with bacterial enzymes suggests that a mammalian endoproteinase Asp‐N might be involved in the formation of AcSDKP through the specific cleavage of the ⁴Pro‐⁵ Asp peptide bond of T β₄.