As noted on the previous page, in Pisum sativum and Nicotiana tabacum DHQ dehydratase (dehydroquinase) [EC 4.4.1.10] occurs as a bifunctional enzyme, with dehydroquinase and shikimate dehydrogenase [EC 1.1.1.25] activities (Deka et al, 1994; Bonner and Jensen, 1994).

Full-length cDNA clones encoding shikimate kinase [EC 2.7.1.71] have been isolated from tomato (Lycopersicon esculentum) (Schmid et al, 1992). The N-terminal portion of the deduced amino acid sequence resembles known chloroplast-specific transit peptides (Schmid et al, 1992). Consistent with this, the in vitro synthesized peptide was imported into and processed to the mature enzyme by isolated chloroplasts. Only one shikimate kinase gene per haploid genome was identifed in tomato (Schmid et al, 1992).

Bonner CA, Jensen RA 1994 Cloning of cDNA encoding the bifunctional dehydroquinase/shikimate dehydrogenase of aromatic amino acid biosynthesis in Nicotiana tabacum. Biochem. J. 302: 11-14.

Deka RK, Anton IA, Dunbar B, Coggins JR 1994 The characterisation of the shikimate pathway enzyme dehydroquinase from Pisum sativum. FEBS Lett. 349: 397-402.

Schmid J, Schaller A, Leibinger U, Boll W, Amrhein N 1992 The in vitro synthesized tomato shikimate kinase precursor is enzymatically active and is imported and processed to the mature enzyme by chloroplasts. Plant J. 2: 375-383.