@article {866,
	title = {Comparative study of the relationship between monomer structure and reactivity for two polyhydroxyalkanoate synthases.},
	journal = {Appl Microbiol Biotechnol},
	volume = {56},
	year = {2001},
	month = {2001 Jul},
	pages = {131-6},
	abstract = {Using organically synthesized hydroxyalkanoate coenzyme A thioesters, the activities of two short-chain polyhydroxalkanoate (PHA) synthases were investigated--Ralstonia eutropha PHA synthase (a type I PHA synthase) and Ectothiorhodospira shaposhnikovii PHA synthase (a type III synthase). The results indicate that the two synthases have similar activities towards most of the monomers tested. 3-Hydroxybutyryl CoA was found to be the most efficient substrate for both synthases. Changes in the side-chain length of the monomers affect monomer reactivity, with shortening of the side-chain length having the more severe effect. Hydrophobicity in the side chain appears to play an important role in the catalytic reaction. The configuration and the position of the hydroxyl group also affect the reactivity of a monomer. Monomers with the [S] configuration can not be recognized by either synthase. Moving the hydroxyl group from the beta carbon to the alpha carbon has a much more severe effect on the reactivity of the monomer than moving the hydroxyl group to the gamma carbon. The results demonstrate that the in vitro system can be used to prepare entirely novel polymers that may not be obtainable from living cells because of metabolic restrictions.},
	keywords = {Acyl Coenzyme A, Acyltransferases, Structure-Activity Relationship, Substrate Specificity},
	issn = {0175-7598},
	author = {Zhang, S and Kamachi, M and Takagi, Y and Lenz, R W and Goodwin, S}
}
@article {868,
	title = {Characterization, seasonal occurrence, and diel fluctuation of poly(hydroxyalkanoate) in photosynthetic microbial mats.},
	journal = {Appl Environ Microbiol},
	volume = {66},
	year = {2000},
	month = {2000 Oct},
	pages = {4279-91},
	abstract = {In situ poly(hydroxyalkanoate) (PHA) levels and repeating-unit compositions were examined in stratified photosynthetic microbial mats from Great Sippewissett Salt Marsh, Mass., and Ebro Delta, Spain. Unlike what has been observed in pure cultures of phototrophic bacteria, the prevalence of hydroxyvalerate (HV) repeating units relative to hydroxybutyrate (HB) repeating units was striking. In the cyanobacteria-dominated green material of Sippewissett mats, the mole percent ratio of repeating units was generally 1HB:1HV. In the purple sulfur bacteria-dominated pink material the relationship was typically 1HB:2HV. In Sippewissett mats, PHA contributed about 0.5 to 1\% of the organic carbon in the green layer and up to 6\% in the pink layer. In Ebro Delta mats, PHA of approximately 1HB:2HV-repeating-unit distribution contributed about 2\% of the organic carbon of the composite photosynthetic layers (the green and pink layers were not separated). Great Sippewissett Salt Marsh mats were utilized for more extensive investigation of seasonal, diel, and exogenous carbon effects. When the total PHA content was normalized to organic carbon, there was little seasonal variation in PHA levels. However, routine daily variation was evident at all sites and seasons. In every case, PHA levels increased during the night and decreased during the day. This phenomenon was conspicuous in the pink layer, where PHA levels doubled overnight. The daytime declines could be inhibited by artificial shading. Addition of exogenous acetate, lactate, and propionate induced two- to fivefold increases in the total PHA levels when applied in the daylight but had no effect when applied at night. The distinct diel pattern of in situ PHA accumulation at night appears to be related, in some phototrophs, to routine dark energy metabolism and is not influenced by the availability of organic nutrients.},
	keywords = {Alkanes, Biofilms, Hydroxybutyrates, Massachusetts, Photosynthesis, Seasons, Spain, Valerates, Water, Water Microbiology},
	issn = {0099-2240},
	author = {Rothermich, M M and Guerrero, R and Lenz, R W and Goodwin, S}
}
