We report on the mechanistic investigation of alkaline phosphatase (AP) triggered self-assembly and hydrogelation of Fmoc-tyrosine (Fmoc-Y). We studied separately the biocatalytic conversion using HPLC, changes in supramolecular interactions and chirality using CD and fluorescence spectroscopy, nanostructure formation by AFM and gelation by oscillatory rheometry. Three consecutive stages could be distinguished (which may overlap, depending on the enzyme concentration). Typically, the phosphorylated Fmoc-Y (Fmoc-pY) undergoes rapid and complete dephosphorylation, followed by formation of aggregates which reorganise into nanofibres and consequently give rise to gelation. We observed a remarkable enhancement of catalytic activity during the early stages of the self-assembly process, providing evidence for enhancement of enzymatic activation by the supramolecular structures formed. Overall, this study provides a further step in understanding biocatalytic self-assembly. © 2013 The Royal Society of Chemistry.