An evaluation of the action of thioesterases on the surface of wool

The thioesterase activity of palmitoyl protein thioesterase (PPT1) and six commercial lipases was measured against the synthetic substrates, S-palmitoyl-N-acetylcysteamine (Ac-Cym-Pal) and S-(18-methyleicosanoyl)-N-acetylcysteamine (Ac-Cym-18-MEA). PPT1 showed good activity against Ac-Cym-Pal but relatively low activity against the longer chain substrate, Ac-Cym-18-MEA. The highest activity was given by Lipolase 100L type EX (Novozyme) and Lipoprotein Lipase (Sigma) with greater than 90% hydrolysis of Ac-Cym-18-MEA within 10 min at pH 7.4. Other lipases to show high levels of thioesterase activity include Lipex 100L (Novozyme), Lipomod 34P (Biocatalysts) and Lipozyme CALB L (Novozyme). Chemical analysis of wool fibre and fabric treated with the above enzymes under optimal conditions showed that there was no hydrolysis of 18-MEA or other covalently bound fatty acids from the fibre surface. No change in the wettability of the fabric surface was observed following enzyme treatments. Scanning electron micrographs of the fabric treated with the most active enzyme, Lipolase 100L type EX, revealed that the surface of the fibres appeared to have a coating that was not removed by extensive extraction. Reasons for the inability of PPT1 and the other esterases to hydrolyse 18-MEA from the wool fibre surface are discussed.     

The chemical composition of wool. XV. The cell membrane couplex.

The cell membrane complex of wool has been examined by electron microscopy of stained cross sections after immersion of the wool in formic acid. The cell membrane complex of the cortex is considerably modified by the treatment, but that of the cuticle appears unchanged. Resistant membranes from cuticle cells, cortical cells and wool have been prepared by treatment with performic acid-ammonia. Amino acid analyses show that the resistant membranes from the cuticle contain citrulline but those from cortical cells do not. It is concluded that the cell membrane complex of the cuticle differs from that of the cortex. Because of the high lysine content of the resistant membranes, their resistance to chemical attack, the hydrophobicity of epicuticle and the observation of a small amount of epsilon-(gamma-glutamyl)lysine, it is postulated that the resistant membranes may contain an appreciable amount of epsilon-(gamma-glutamyl)lysine cross links.     

The action of ATP on natural actomyosin.

1. When ATP is added to Limulus myosin B and the mixture is centrifuged at 50,000 rev/min for 3 hr to dissociate it into a supernatant of myosin and a pellet of actin, the results are contrary to expectation. The pellet does contain actin but no more than one obtains if the ATP is omitted. The supernatant also contains actin. 2. If this is done in the Model E centrifuge, the major peak disappears upon ATP addition and a new peak, sedimenting at a rate typical of myosin, appears. When only this slow moving peak is run on SDS gels, actin is clearly seen. 3. It is concluded that ATP does not dissociate this actomyosin but rather causes a conformational change.