Figure 2.

Spectroscopic Analysis of CAS and OASS.

(A) Absorption spectra of PLP in Gm-CAS alone (black) and after addition of 100 μM Cys (blue), 1 mM O-acetylserine (orange), or 1 mM β-cyanoalanine (red). a.u., arbitrary units.

(B) Absorption spectra of PLP in Gm-OASS alone (black) and after addition of 1 mM Cys (blue), 100 μM O-acetylserine (orange), or 1 mM β-cyanoalanine (red).

(C) Proposed catalytic cycle for CAS showing the initial Schiff base form of PLP (A_max = 412 nm), formation of the α-aminoacrylate intermediate (A_max = 470 nm) after the first half reaction, nucleophilic attack in the second half reaction leading to the external aldimine (A_max = 418 nm), and release of product.