Geotrichum candidum NRRL Y-553 lipase: purification, characterization and fatty acid specificity.

Lipases from Geotrichum candidum NRRL Y-553 are of interest because of their unique specificity for cis-9-unsaturated fatty acids relative to both stearic and palmitic acids. The lipases were partially purified by chromatography on Octyl Sepharose, AG MP-1 macroporous anion exchanger, and chromatofocusing resin. The preparation was found to contain multiple, glycosylated lipases varying slightly in pI (pI 4.88, 4.78, 4.65, 4.57 and 4.52) as judged by both activity and silver staining. The molecular mass determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis was 64 kilodaltons for the main species, with minor species of 60 and 57 kilodaltons present as well. The specificity of the crude lipases for hydrolysis of 4-methylumbelliferyl esters of oleic vs. palmitic acid was 20-to-1. The specificity of the purified, partially separated lipases was similar to that of the crude preparation. Thus the lipases could be used even in crude form for the hydrolysis and restructuring of triacylglycerols on a large scale.

Methyl-branched octanoic acids as substrates for lipase-catalyzed reactions.

Hydrolyses of racemic methyl-branched octanoic acid thiolesters are described using six commercial lipases as catalysts. Branching at positions 2, 4 and 5 greatly reduced activity; branching at the 3-position virtually eliminated activity. The reactivities of the racemic branched thiolesters relative to the unbranched ester were very similar for each lipase preparation examined. In reactions involving configurationally pure 2-methyloctanoic acids, the S-enantiomer reacted faster both in esterification of aliphatic alcohols and in hydrolyses of aliphatic alcohol esters with all of the lipases examined. Stereobiases in hydrolyses of the octanoic acid esters branched at other positions were low and variable. In sharp contrast to the hydrolyses of the thiolesters of 2-methyloctanoic acid, two aryl esters of 2-methyloctanoic acid catalyzed by R. miehei lipase hydrolyzed with a bias for the R-configuration. A view of the ester-enzyme complex is offered to explain the relative rates of reaction of the racemic esters.

Purification and specificity of lipases fromGeotrichum candidum.

A crude, commercialGeotrichum candidum lipase (EC 3.1.1.3) preparation (Amano GC-20) was purified by hydrophobic interaction chromatography on Octyl Sepharose. The purified enzyme is a microheterogeneous glycoprotein containing isozymes varying in molecular weight, pI and specificity. It consists of 64, 62 and 59 kDa species as determined by denaturing polyacrylamide gel electrophoresis. Five isozymes (pI 4.40, 4.47, 4.58, 4.67 and 4.72) are detected by isoelectric focusing using both silver and activity stains. Chromatofocusing was used to separate the isozymes according to pI. Although all the isozymes are specific for oleatevs stearate esters, one isozyme (pI 4.72) is also specific for oleatevs palmitate. The number of isozymes is reduced to two (pI 4.67 and 4.72) after carbohydrate removal using endoglycosidase F/N-glycosidase. These isozymes may be products of two lipase genes.

Kinetic resolution of secondary alcohols with commercial lipases : Application to rootworm sex pheromone synthesis.

The relative rates of enzyme-catalyzed esterification of the enantiomers of 2-octanol with various acids were determined for several commercial lipases. Interesterifications and hydrolyses of racemic 2-octanol esters catalyzed by these enzymes were also examined. Novo'sMucor miehei lipase exhibited considerable enantioselectivity and was therefore employed to prepare 8-methyl-2-decanols with high configurational purity at the carbinol carbon. Esters of these alcohols had been previously identified as sexually attractive to several rootworm (Diabrotica) species, and the stereochemistry of those esters had been shown to be critical to the attraction. The enzymatic resolution provides a convenient method to obtain such esters in a desired state of configurational purity.

[Determining a level of immigration for Quebec: why and how?]. / Determiner un niveau d'immigration pour le Quebec: pourquoi, comment?

PIP: In the late 1960s, Quebec demonstrated its willingness to influence migration by creating a Ministry of Immigration. The goal of the Ministry changed over the course of a decade from assuring harmonious integration of immigrants to obtaining a greater role in recruitment and selection as well as in reception and establishment. In the early 1970s the Canadian government undertook a significant revision of its immigration policies. The most significant change was probably the requirement of an annual estimate of the number of immigrants judged opportune to admit during a particular time period. to be preceded by consultations with the provinces concerning demographic needs and the labor market. A 1978 agreement between Quebec and the Canadian government gave Quebec a greater role in immigrant selection and recruitment, and in effect allowed it to develop its own immigration policy. Ability to absorb potential immigrants became the primary criterion in setting quotas for Quebec. The approach of the federal government has not changed greatly since the new policy came into use. The extent of annual net immigration judged desirable has changed from about 75,000 persons initially to about 55,000 more recently. The federal government has always viewed immigration as a possible solution to labor market problems, but estimates of manpower needs became very volatile in the late 1970s with the general rise in rates of unemployment, and survey results lost importance as a source of guidance. The government estimated that 20 to 25 thousand immigrants selected to fill specific manpower needs could be accomodated annually in the 1980s, but the collapse of the labor market following the economic crisis caused a downward revision in estimates for 1982-83 to 8000 to 10,000 workers with jobs already in hand. In order to participate in planning of immigration, Quebec had to develop a research program desinged to identify its capacity to absorb immigrants each year. The 1st step was to try to measure the impact of immigration using a framework of demoeconomic projections aided by a behavior model. 3 levels of immigration ranging from 15,000 to 30,000 annually were compared to a control case of no immigration in order to detect impact. Growth contributed by immigration is not expected to help solve the 3 major demographic problems expected over the next 20 years: the fertility decline, aging of the population, and emigration. Immigration does however exacerbate unemployment although it does not cause it. Economic constraints on immigration in the early 1980s are due more to poor prospects of growth than to the impact of immigration on growth. The suggested numbers of immigrants of 15,200 in 1983, 16,000 in 1984, and 17,000 in 1985 almost constitute minima given the probable immigration of family members and refugees.^ieng

[The demographic situation of Quebec at the time of the referendum]. / La situation demographique du Quebec a l'heure du referendum

PIP: The authors present a review of the demographic situation in Quebec at the time of the 1980 referendum on the future of the province. They discuss linguistic composition and trends in Quebec and the rest of Canada, the prospect of slowing population growth in Quebec, and the relative size of Quebec's population in relation to that of Canada as a whole^ieng