5.4.3.8 L-glutamate 1-semialdehyde = 5-aminolevulinate catalytic mechanism via external aldimine and Gem-diamine intermediates, overview 727125 5.4.3.8 L-glutamate 1-semialdehyde = 5-aminolevulinate enzyme shows an active-site gating loop, which undergoes a dramatic conformational change during catalysis, that is simultaneously open in one subunit and closed in the other. Loop movement requires a beta-sheet-to-alpha-helix transition to assume the closed conformation, thus facilitating transport of substrate toward, and concomitantly forming, an integral part of the active site. The accompanying intersubunit cross-talk controls negative cooperativity between the allosteric pair 682509 5.4.3.8 L-glutamate 1-semialdehyde = 5-aminolevulinate intermolecular transamination occurs during conversion of (S)-4-amino-5-oxopentanoate to 5-amino-4-oxopentanoate 3424 5.4.3.8 L-glutamate 1-semialdehyde = 5-aminolevulinate mechanism 3442 5.4.3.8 L-glutamate 1-semialdehyde = 5-aminolevulinate ping-pong bi-bi mechanism in which 4,5-diaminovalerate is the second substrate and 4,5-dioxovalerate is an alternative first substrate 3441 5.4.3.8 L-glutamate 1-semialdehyde = 5-aminolevulinate the catalytic mechanism includes enzyme-bound diaminovalerate as a central intermediate 3439 5.4.3.8 L-glutamate 1-semialdehyde = 5-aminolevulinate wild-type enzyme and gabaculine-resistant mutant enzyme use a ping-pong bi-bi mechanism in which 4,5-diaminovalerate is a likely intermediate 3430