Activated Tetramers of Phenylalanine Hydroxylase

Phenylalanine hydroxylase (PAH) is a dynamic, allosterically regulated tetramer whose malfunction underlies the metabolic disorder phenylketonuria (PKU). Understanding how PAH samples different quaternary and conformational states—and how these states shift in response to ligand binding or disease-associated mutations—requires an integrative biophysical strategy. In this webinar, we will explore how mass photometry, analytical ultracentrifugation (AUC), SEC-MALS, SEC-SAXS, and time-resolved SAXS collectively define a two-state quaternary landscape for PAH and reveal how structural transitions drive enzyme activation. These solution-based approaches converge with newly determined cryo-electron microscopy structures that visualize key regulatory domain movements and provide atomic insight into allosteric switching. Together, these complementary methods illustrate a modern, multi-modal framework for dissecting the structural and functional mechanisms of complex, heterogeneous enzymes and highlight how biophysical integration advances our understanding of PAH regulation and PKU-associated dysfunction.

3 Key Takeaways 

1. Applications of mass photometry during purification of recombinant enzymes.
2. The importance of understanding oligomeric state of structural biology targets.
3. The complementarity of mass photometry to cryo-electron microscopy studies versus other biophysical measures.