CLONING AND CHARACTERIZATION OF ZYMOMONAS-MOBILIS GENES ENCODING EXTRACELLULAR LEVANSUCRASE AND INVERTASE

The genes encoding the extracellular levansucrase and invertase of Zym omonas mobilis have been cloned and sequenced, The levansucrase gene, sucZE2, spans 1269 bp and encodes an M(r) 46,790 polypeptide, and the invertase gene, sucZE3, is of 1239bp and encodes an M(r) 46,110 polype ptide, The 5'-terminal sequences of both genes corresponded to the N-t erminal amino acid sequences of the secreted levansucrase and invertas e, implying that the secretion of both enzymes does not involve proteo lytic processing of the N-terminals. Both enzyme molecules appear to c arry no typical N-terminal secretion signal, Significant homology betw een sucZE2 and sucZE3 was observed, but both genes showed no homology to the gene encoding an intracellular invertase coexisting in Z. mobil is. Two genes, sucZE2 and sucZE3, are possibly placed in an operon bec ause the expression of two genes were simultaneously controlled by the regulator gene zliE, previously identified.