A critical analysis of kinetic data of 3-hexulosephosphate synthases. Michaelis-Menten or complex characteristics.

Investigations of the 3-hexulosephosphate synthase (HPS) from different methylotrophic bacteria have revealed apparent discrepancies in kinetic behaviour. In all methanol-utilizing species investigated by us the kinetic characteristics showed intermediary plateau regions. Therefore, this behaviour is assumed to be a general feature of the HPS from all non-methane-utilizing methylotrophic bacteria. However, this assumption is in contrast to the results of other authors. Both for Methylomonas M15 (SAHM et al. 1976) and Methylomonas aminofaciens 77a (KATO et al. 1977, 1978) MICHAELIS-MENTEN kinetics of the HPS were stated. To check the validity of our assumption we have analyzed the kinetic data given by others. Indications of the existence of intermediary plateau regions could be found with the enzyme from Arthrobacter globiformis (BYKOVSKAYA and VORONKOV 1977) and Methylomonas aminofaciens 77a (KATO et al. 1978). Furthermore, biphasic ARRHENIUS plots indicate a multiple character of the HPS from these species as could already be demonstrated with the enzyme from Bacterium MB 58 and Pseudomonas oleovorans. In addition, causes which may obscure the detection of intermediary plateau regions are demonstrated.