Pseudomonas putida, pyridine

Pyridine-2,6-di(monothiocarboxylic acid) (Fig. 26, 73) [for a review, see 36), cf. also (37)] was obtained from Pseudomonas putida (262) and later from Pseudomonas stutzeri (203). It forms a brown Fe " complex and a blue Fe " complex (both FeLig2) (343), wbicb may be accompanied by complexes carrying two additional cyanide ions (345). An X-ray analysis (Plate 6) of tbe Fe " complex of 73 shows a distorted octahedral symmetry (343). There is evidence that a sulfenic acid residue (-CO-SOH) is the biosynthetic link between -COOH and -COSH (344). 

Several structures of LipDHs have been determined by X-ray diffraction, including a structure from Pseudomonas putida, solved to 2.45 A resolution. The enzyme from P. putida consists of two identical subunits — as do all LipDHs — each of molecular mass 48 159 Da, and is only active as a dimer. Each subunit contains four domains. The largest domain binds FAD and is in contact with the other three domains an NAD-binding domain, a central domain, and an interface domain. The active site of one subunit of LipDH is shown in Figure 7. In addition to the FAD cofactor, it contains the disulfide bond formed by conserved cysteine residues 43 and 48, as well as Tyrl81, which covers the NAD -binding pocket in the absence of the pyridine cofactor,... 

A number of heteroaromatic monothiocarboxylic acids are formed by Pseudomonas sp. From P. putida, there was isolated pyridine-2,6-di-(mon-othiocarboxylic acid) 46 (Scheme 16). Of interest is the fact that in P. stutzeri KC, a copper complex of 46 is the active agent for a one electron transfer in the bacterial biodegradation of CCI4. Methylation of P. putida extracts provides a number of related structures such as 47. In addition, a P. fluorescens sp. contains 8-hydroxy-4-methoxy-quinoline-2-monothiocarboxylic acid 48.98... 

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