A monoclonal antibody obtained by immunization of mice with heat-killed cells of Listeria monocytogenes serotype 4d showed reactivity towards a protein (P45) from L. monocytogenes with an apparent molecular mass of 45 kDa. This protein was detected in the culture supernatant and at the cell surface of L. monocytogenes. Proteins cross-reacting with the monoclonal antibody were present in all Listeria strains investigated, except L. grayi. The structural gene was cloned in Escherichia coli and sequenced. Translation of the gene starts at a TTG initiation codon. The gene was found to code for a protein of 402 amino acid residues with a predicted molecular mass of 42.7 kDa. It has a signal peptide of 27 amino acid residues, resulting in a molecular mass for the mature polypeptide of 39.9 kDa. Protein database searches showed that this protein has 55% similarity and 38% identity to protein p60 of L. monocytogenes and exhibits significant sequence similarities to p54 from Enterococcus faecium and Usp45 from Lactococcus lactis. P45 was shown to have peptidoglycan lytic activity and the encoding gene was named spl (secreted protein with lytic property).

The aim of the present study was to identify and quantitatetrans isomers of C18 fatty acids in some French infant formulas. Twenty powdered infant formulas were purchased in pharmacies and supermarkets in order to assess theirtrans mono‐ and poly‐unsaturated fatty acids content. The fatty acid profiles were examined using methyl and isopropyl ester derivatives. The combination of gas‐liquid chromatography, high‐performance liquid chromatography, and silver nitrate thin‐layer chromatography was needed to describe the detailed fatty acid compositions of the samples, includingtrans isomers of unsaturated C18 fatty acids. All the samples containedtrans isomers of C18∶1 acid (mean level 1.97±0.28% of total fatty acids), with vaccenic acid being generally the major isomer (15 out of 20 samples), thus indicating the origin from bovine milk. All the formulas also contained various isomers of linoleic and α‐linolenic acids, but at lower levels.Trans PUFA isomers are the same as those present in deodorized oils. In conclusion, all the infant formulas analyzed in this study contained sometrans fatty acids, including isomers of essential fatty acids. This should be taken into account in the dietary intake of the newborn.

Several years ago, it was established that the delta 15 trans isomer of alpha-linolenic acid is converted in vivo into fatty acids containing 20 and 22 carbons (geometrical isomers of eicosapentaenoic and docosahexaenoic acids). The present study focused on the in vitro delta 6 desaturation, the first step of the biosynthesis of the n-3 long-chain polyunsaturated fatty acids from 18:3n-3. For that purpose, rat liver microsomes were prepared and incubated with radiolabeled 18:3 delta 9cis,12cis,15cis (18:3c,c,c) or 18:3 delta 9cis, 12cis, 15trans (18:3c,c,t) under desaturation conditions. The data show that 18:3c,c,t is converted at a lower rate compared with alpha-linolenic acid. The product of conversion of 18:3c,c,t may be 18:4 delta 6cis, 9cis, 12cis, 15trans resulting from a delta 6 desaturation of the trans substrate. Moreover, the conversion of radiolabeled 18:3c,c,t was strongly decreased by the presence of 18:3c,c,c (up to 48%) while the 18:3c,c,t only slightly decreased the conversion of radiolabeled 18:3c,c,c. Thus, the desaturation enzyme presented a higher affinity for the native all-cis n-3 substrate.