Fig. 2.

ESI-MS analysis of the reaction products of DauA and DauB. (A and C) Analysis of reaction mixtures with active DauA without (A) or with (C) catalase. (E) Analysis of reaction mixture with active DauB. (B, D, and F) Corresponding controls with heat-denatured DauA or DauB. The signals with m/z values of 146.1, 175.2, and 174.1 were in accordance with the positive ions of 4-guanidinobutyric acid (4-GBA; A and C), d-arginine (D-Arg; A–D), or l-arginine (L-arg; E), and 2-ketoarginine (2-KA; C and F).