Thioester Linkage Research Articles

Palmitoyl-protein thioesterase-1 deficiency leads to the activation of caspase-9 and contributes to rapid neurodegeneration in INCL

The infantile neuronal ceroid lipofuscinosis (INCL), a rare (one in 100 000 births) but one of the most lethal inherited neurodegenerative storage disorders of childhood, is caused by inactivating mutations in the palmitoyl-protein thioesterase-1 (PPT1) gene. PPT1 cleaves thioester linkages in s-acylated (palmitoylated) proteins and facilitates their degradation and/or recycling. Thus, PPT1-deficiency leads to an abnormal intracellular accumulation of s-acylated proteins causing INCL pathogenesis. Although neuronal apoptosis is the suggested cause of neurodegeneration in this disease, the molecular mechanism(s) remains poorly understood. We recently reported that one of the major pathways of neuronal apoptosis in PPT1-knockout (PPT1-KO) mice that mimic INCL, is mediated by endoplasmic reticulum (ER) stress-induced caspase-12 activation. ER stress also increases the production of reactive oxygen species (ROS), disrupts Ca(2+) homeostasis and increases the potential for destabilizing mitochondrial membrane. Mitochondrial membrane destabilization activates caspase-9 present in this organelle, and can mediate apoptosis. We report here that the levels of superoxide dismutase (SOD), most likely induced by ROS, in human INCL as well as PPT1-KO mouse brain tissues are markedly elevated. Moreover, we demonstrate that activated caspase-3 and cleaved-PARP, indicative of apoptosis, are also increased in these tissues. Using cultured neurospheres from PPT1-KO and wild-type mouse fetuses, we further demonstrate that the levels of ROS, SOD-2, cleaved-caspase-9, activated caspase-3 and cleaved-PARP are elevated. We propose that: (i) ER stress due to PPT1-deficiency increases ROS and disrupts calcium homeostasis activating caspase-9 and (ii) caspase-9 activation mediates caspase-3 activation and apoptosis contributing to rapid neurodegeneration in INCL.

Endoplasmic Reticulum Stress‐Mediated Caspase‐4 Activation and Apoptosis Lead to Neurodegeneration in INCL

Infantile Neuronal Ceroid Lipofuscinosis (INCL), commonly known as infantile Batten disease, is a rare, uniformly fatal, progressive encephalopathy of children. Inactivating mutations in the gene encoding palmitoyl-protein thioesterase-1 (PPT1) is the molecular basis of INCL. PPT1 is a lysosomal enzyme that cleaves thioester linkages in s-acylated proteins. Due to the lack of PPT1 enzymatic activity, the palmitic acid linked to these proteins is not removed and as a result, the lipid-modified proteins are not degraded or recycled. Although apoptosis is the suggested cause of neuronal death in INCL neither the molecular mechanisms of apoptosis nor the reasons for rapid brain atrophy are defined. Understanding the molecular mechanisms of neuronal apoptosis would facilitate the development of therapeutic approaches to this disease. Using cultured cells and autopsy brain samples from INCL patients, we discovered that these cells undergo endoplasmic reticulum (ER) stress attested by the expression of canonical ER-stress marker protein, Grp-78, at a high level. To confirm these results we induced the expression of GFP-tagged GAP-43, a palmitoylated protein in INCL and normal cells to determine the cellular localization of this protein. We found that while GFP-GAP-43 is diffusely distributed in normal cells, it is abnormally accumulated in the ER-Golgi region of the INCL cells. We also found that in INCL cells ER stress mediates activation of caspase-4, which leads to caspase-3 activation and apoptosis. Most importantly, we found that inhibition of caspase-4 activity by a specific inhibitor of this enzyme protects the INCL cells from apoptosis. Our results, for the first time, define a major pathway to apoptosis in INCL providing insight into the pathogenesis of this disease and identify potential targets for therapeutic intervention.

Palmitoylation at Cys595 is essential for PECAM-1 localisation into membrane microdomains and for efficient PECAM-1-mediated cytoprotection

The Ig-ITIM superfamily member, PECAM-1 acts as a negative regulator of ITAM-signalling pathways in platelets involving GPVI/FcR gamma chain and Fc?RIIa. This negative feedback loop involves regulation of collagen and GPVI-dependent aggregation events, platelet-thrombus-growth on immobilised collagen under flow and Fc?RIIa-mediated platelet responses. In this study, we show that PECAM-1 is selectively palmitoylated involving a thioester linkage with an unpaired cysteine residue at amino acid position 595 in its cytoplasmic domain. As palmitoylation is known to target proteins to membrane microdomains, we investigated the microdomain localisation for PECAM-1 in platelets and nucleated cells. In unstimulated platelets, approximately 20% of PECAM-1 is localised to Triton-insoluble microdomain fractions and it does not increase with platelet activation by collagen, collagen-related peptide, thrombin- or human-aggregated IgG. PECAM-1 is in close physical proximity with GPVI in platelet microdomains. Removal of platelet cytoskeleton prior to sucrose-density-gradient separation showed that PECAM-1 was associated with both the Triton-soluble and membrane skeleton in microdomain-associated fractions. Disruption of microdomains by membrane-cholesterol depletion resulted in loss of PECAM-1 localisation to membrane microdomains. Mutational analysis of juxtamembrane cysteine residue to alanine (C595A) of human PECAM-1 resulted in loss of palmitoylation and a sixfold decrease in association with membrane microdomains. Functionally, the palmitoylated cysteine 595 residue is required, in part, for efficient PECAM-1-mediated cytoprotection. These results show that cysteine 595 is required for constitutive association of PECAM-1 with membrane microdomains and PECAM-1-mediated cytoprotection, where it may act as a crucial regulator of signaling and apoptosis events.

Palmitoyl-protein thioesterase-1 deficiency mediates the activation of the unfolded protein response and neuronal apoptosis in INCL

Numerous proteins undergo modification by palmitic acid (S-acylation) for their biological functions including signal transduction, vesicular transport and maintenance of cellular architecture. Although palmitoylation is an essential modification, these proteins must also undergo depalmitoylation for their degradation by lysosomal proteases. Palmitoyl-protein thioesterase-1 (PPT1), a lysosomal enzyme, cleaves thioester linkages in S-acylated proteins and removes palmitate residues facilitating the degradation of these proteins. Thus, inactivating mutations in the PPT1 gene cause infantile neuronal ceroid lipofuscinosis (INCL), a devastating neurodegenerative storage disorder of childhood. Although rapidly progressing brain atrophy is the most dramatic pathological manifestation of INCL, the molecular mechanism(s) remains unclear. Using PPT1-knockout (PPT1-KO) mice that mimic human INCL, we report here that the endoplasmic reticulum (ER) in the brain cells of these mice is structurally abnormal. Further, we demonstrate that the level of growth-associated protein-43 (GAP-43), a palmitoylated neuronal protein, is elevated in the brains of PPT1-KO mice. Moreover, forced expression of GAP-43 in PPT1-deficient cells results in the abnormal accumulation of this protein in the ER. Consistent with these results, we found evidence for the activation of unfolded protein response (UPR) marked by elevated levels of phosphorylated translation initiation factor, eIF2alpha, increased expression of chaperone proteins such as glucose-regulated protein-78 and activation of caspase-12, a cysteine proteinase in the ER, mediating caspase-3 activation and apoptosis. Our results, for the first time, link PPT1 deficiency with the activation of UPR, apoptosis and neurodegeneration in INCL and identify potential targets for therapeutic intervention in this uniformly fatal disease.

Structural Evolution of the Chromophore in the Primary Stages of Trans/Cis Isomerization in Photoactive Yellow Protein

We have studied the structural changes induced by optical excitation of the chromophore in wild-type photoactive yellow protein (PYP) in liquid solution with a combined approach of polarization-sensitive ultrafast infrared spectroscopy and density functional theory calculations. We identify the nuC8-C9 marker modes for solution phase PYP in the P and I0 states, from which we derive that the first intermediate state I0 that appears with a 3 ps time constant can be characterized to have a cis geometry. This is the first unequivocal demonstration that the formation of I0 correlates with the conversion from the trans to the cis state. For the P and I0 states we compare the experimentally measured vibrational band patterns and anisotropies with calculations and find that for both trans and cis configurations the planarity of the chromophore has a strong influence. The C7=C8-(C9=O)-S moiety of the chromophore in the dark P state has a trans geometry with the C=O group slightly tilted out-of-plane, in accordance with the earlier reported structure obtained in an X-ray diffraction study of PYP crystals. In the case of I0, experiment and theory are only in agreement when the C7=C8-(C9=O)-S moiety has a planar configuration. We find that the carboxylic side group of Glu46 that is hydrogen-bonded to the chromophore phenolate oxygen does not alter its orientation on going from the electronic ground P state, via the electronic excited P state to the intermediate I0 state, providing conclusive experimental evidence that the primary stages of PYP photoisomerization involve flipping of the enone thioester linkage without significant relocation of the phenolate moiety.

Dichlorination of a pyrrolyl-S-carrier protein by FADH 2 -dependent halogenase PltA during pyoluteorin biosynthesis

The antifungal natural product pyoluteorin contains a 4,5-dichloropyrrole moiety. The timing of dichlorination in the heteroaromatic ring is now shown to occur after proline is tethered by thioester linkage to the carrier protein PltL and enzymatically desaturated to the pyrrolyl-S-PltL. Surprisingly, the FADH2-dependent halogenase PltA catalyzes chlorination at both positions of the ring, generating the 5-chloropyrrolyl-S-PltL intermediate and then the 4,5-dichloropyrrolyl-S-PltL product. PltA activity strictly depends on a heterologous flavin reductase that uses NAD(P)H to produce FADH2. Electrospray ionization-Fourier transform MS detected five covalent intermediates attached to the 11-kDa carrier protein PltL. Tandem MS localized the site of covalent modification on the carrier protein scaffold. HPLC analysis of the hydrolyzed products was consistent with the regiospecific chlorination at position 5 and then position 4 of the heteroaromatic ring. A mechanism for dichlorination is proposed involving formation of a FAD-4a-OCl intermediate for capture by the electron-rich C4 and C5 of the heteroaromatic pyrrole moiety.

Enzymatic Hydrolysis of Thioester Linkages in Bacterial Poly(3-hydroxybutyrate-co-3-mercaptopropionate)s by Poly(3-hydroxybutyrate) Depolymerase Isolated from Ralstonia pickettii T1

Enzymatic Hydrolysis of Thioester Linkages in Bacterial Poly(3-hydroxybutyrate- co -3-mercaptopropionate)s by Poly(3-hydroxybutyrate) Depolymerase Isolated from Ralstonia pickettii T1

Differential Regulation of AMPA Receptor Subunit Trafficking by Palmitoylation of Two Distinct Sites

Modification of AMPA receptor function is a major mechanism for the regulation of synaptic transmission and underlies several forms of synaptic plasticity. Post-translational palmitoylation is a reversible modification that regulates localization of many proteins. Here, we report that palmitoylation of the AMPA receptor regulates receptor trafficking. All AMPA receptor subunits are palmitoylated on two cysteine residues in their transmembrane domain (TMD) 2 and in their C-terminal region. Palmitoylation on TMD 2 is upregulated by the palmitoyl acyl transferase GODZ and leads to an accumulation of the receptor in the Golgi and a reduction of receptor surface expression. C-terminal palmitoylation decreases interaction of the AMPA receptor with the 4.1N protein and regulates AMPA- and NMDA-induced AMPA receptor internalization. Moreover, depalmitoylation of the receptor is regulated by activation of glutamate receptors. These data suggest that regulated palmitoylation of AMPA receptor subunits modulates receptor trafficking and may be important for synaptic plasticity.

A Method of Mapping Protein Sumoylation Sites by Mass Spectrometry Using a Modified Small Ubiquitin-like Modifier 1 (SUMO-1) and a Computational Program

Post-translational modification by small ubiquitin-like modifier 1 (SUMO-1) is a highly conserved process from yeast to humans and plays important regulatory roles in many cellular processes. Sumoylation occurs at certain internal lysine residues of target proteins via an isopeptide bond linkage. Unlike ubiquitin whose carboxyl-terminal sequence is RGG, the tripeptide at the carboxyl terminus of SUMO is TGG. The presence of the arginine residue at the carboxyl terminus of ubiquitin allows tryptic digestion of ubiquitin conjugates to yield a signature peptide containing a diglycine remnant attached to the target lysine residue and rapid identification of the ubiquitination site by mass spectrometry. The absence of lysine or arginine residues in the carboxyl terminus of mammalian SUMO makes it difficult to apply this approach to mapping sumoylation sites. We performed Arg scanning mutagenesis by systematically substituting amino acid residues surrounding the diglycine motif and found that a SUMO variant terminated with RGG can be conjugated efficiently to its target protein under normal sumoylation conditions. We developed a Programmed Data Acquisition (PDA) mass spectrometric approach to map target sumoylation sites using this SUMO variant. A web-based computational program designed for efficient identification of the modified peptides is described.

Analysis of hair lipids and tensile properties as a function of distance from scalp

Cuticle cells form the outer covering surrounding and protecting the cortex. The cuticle cells are thin, flat and overlap, and intercellular lipid lamellae are found in the gaps between the cell boundaries. The lipid lamellae are also found within the cortex in the cell boundaries between the long fribrous corticle cells. In addition, the outer surfaces of the cuticle cells are covered by a monolayer of covalently bound fatty acids, a major component of which is 18-methyleicosanoic acid. The fatty acids are thought to be attached through thio-ester linkages. Together these lipids are thought to be major determinants of the physical properties of the hair. The present study tested the hypothesis that both free and covalently bound lipids are progressively lost during normal environmental exposures. This progressive loss within the cuticle layers may, in part, lead to an increased susceptibility of the protein and lipid lamellae in the cortex to degradation. This degradation, in turn, would contribute to a progressive decrease in the tensile properties of the hair. Research grade hair was cut into five segments from the root to the distal end. Lipids from each segment were extracted and analyzed by thin-layer chromatography in conjunction with photodensitometry. The major free polar lipid classes in the hair included ceramides, glucosylceramides and cholesterol sulfate. The concentrations of all of the free polar lipids as well as the covalently bound fatty acids decreased in going from the root to the distal end of the hair. In addition, there was a significant reduction in tensile properties of the hair from the root to distal end. In conclusion, the progressive loss of endogenous free and covalently bound lipids from hair, which are probably related to normal weathering of the hair and grooming practices, may help contribute to a marked decrease in tensile properties to the hair.

A simple and efficient method to prepare thioesters in aqueous solutions

A simple method is described for the efficient synthesis of biologically-active thioesters in aqueous solutions. The method utilizes imidazole as a catalyst and easily synthesized acyl or aminoacyl adenylates to synthesize a variety of thioesters, from small molecules to macromolecules. Yields in excess of 90% can be achieved in less than 10 min at room temperature. Specifically, functional derivatization of RNA with biotin via thioester linkage is demonstrated.

The human Kv1.1 channel is palmitoylated, modulating voltage sensing: Identification of a palmitoylation consensus sequence

Voltage-dependent K(+) channels rely on precise dynamic protein interactions with surrounding plasma membrane lipids to facilitate complex processes such as voltage sensing and channel gating. Many transmembrane-spanning proteins use palmitoylation to facilitate dynamic membrane interactions. Herein, we demonstrate that the human Kv1.1 ion channel is palmitoylated in the cytosolic portion of the S(2)-S(3) linker domain at residue C243. Through heterologous expression of the human Kv1.1 protein in Sf9 cells, covalent radiolabeling with [(3)H]palmitate, chemical stability studies of the [(3)H]-palmitoylated protein, and site-directed mutagenesis, C243 was identified as the predominant site of palmitoylation. The functional sequelae of palmitoylation were examined by analysis of whole cell currents from WT and mutant channels, which identified a 20-mV leftward shift in the current-voltage relationship when palmitoylation at C243 (but not with other cysteine deletions) is prevented by site-directed mutagenesis, implicating a role for palmitoylated C243 in modulating voltage sensing through protein-membrane interactions. Database searches identified an amino acid palmitoylation consensus motif (ACP/RSKT) that is present in multiple other members of the Shaker subfamily of K(+) channels and in several other unrelated regulatory proteins (e.g., CD36, nitric oxide synthase type 2, and the mannose-6 phosphate receptor) that are known to be palmitoylated by thioester linkages at the predicted consensus site cysteine residue. Collectively, these results (i) identify palmitoylation as a mechanism for K(+) channel interactions with plasma membrane lipids contributing to electric field-induced conformational alterations, and ii) define an amino acid consensus sequence for protein palmitoylation.

Cloning, Expression, and Characterization of the Human Mitochondrial β-Ketoacyl Synthase: COMPLEMENTATION OF THE YEAST CEM1 KNOCK-OUT STRAIN

A human beta-ketoacyl synthase implicated in a mitochondrial pathway for fatty acid synthesis has been identified, cloned, expressed, and characterized. Sequence analysis indicates that the protein is more closely related to freestanding counterparts found in prokaryotes and chloroplasts than it is to the beta-ketoacyl synthase domain of the human cytosolic fatty acid synthase. The full-length nuclear-encoded 459-residue protein includes an N-terminal sequence element of approximately 38 residues that functions as a mitochondrial targeting sequence. The enzyme can elongate acyl-chains containing 2-14 carbon atoms with malonyl moieties attached in thioester linkage to the human mitochondrial acyl carrier protein and is able to restore growth to the respiratory-deficient yeast mutant cem1 that lacks the endogenous mitochondrial beta-ketoacyl synthase and exhibits lowered lipoic acid levels. To date, four components of a putative type II mitochondrial fatty acid synthase pathway have been identified in humans: acyl carrier protein, malonyl transferase, beta-ketoacyl synthase, and enoyl reductase. The substrate specificity and complementation data for the beta-ketoacyl synthase suggest that, as in plants and fungi, in humans this pathway may play an important role in the generation of octanoyl-acyl carrier protein, the lipoic acid precursor, as well as longer chain fatty acids that are required for optimal mitochondrial function.

Characterization of the Formation of the Pyrrole Moiety during Clorobiocin and Coumermycin A1 Biosynthesis

The aminocoumarin antibiotics clorobiocin and coumermycin A(1) target the B subunit of DNA gyrase by presentation of the 5-methyl-pyrrolyl-2-carboxy ester moiety in the ATP-binding site of the enzyme. The pyrrolyl pharmacophore is derived by a four electron oxidation of a prolyl unit while tethered in phosphopantetheinyl thioester linkage to a peptidyl carrier protein (PCP) subunit. l-Proline is selected and activated as l-prolyl-AMP by adenylation domain enzymes (CloN4 and CouN4) and then installed as the thioester on the holo form of the PCP proteins CloN5 and CouN5. Enzymatic oxidation of the prolyl-S-PCP by the flavoprotein dehydrogenase CloN3 can be followed by rapid quench and subsequent electrospray ionization-Fourier transform mass spectrometry analysis of the acyl-S-protein substrate/product mixture to establish that a two-electron oxidized pyrrolinyl-S-enzyme transiently accumulates on the way to the four-electron oxidized, heteroaromatic pyrrolyl-2-carboxy-S-PCP acyl enzyme product.

Expanding diversity in dynamic combinatorial libraries: simultaneous exchange of disulfide and thioester linkages

Dynamic combinatorial libraries have been prepared which feature two simultaneous covalent exchange reactions in aqueous solution at neutral pH. This allows for diversity, not only of the subunits that are linked, but also of the linkage itself.

Influence of acylation sites of influenza B virus hemagglutinin on fusion pore formation and dilation.

The cytoplasmic tail (CT) of hemagglutinin (HA) of influenza B virus (BHA) contains at positions 578 and 581 two highly conserved cysteine residues (Cys578 and Cys581) that are modified with palmitic acid (PA) through a thioester linkage. To investigate the role of PA in the fusion activity of BHA, site-specific mutagenesis was performed with influenza B virus B/Kanagawa/73 HA cDNA. All of the HA mutants were expressed on Cos cells by an expression vector. The membrane fusion ability of the HA mutants at a low pH was quantitatively examined with lipid (octadecyl rhodamine B chloride) and aqueous (calcein) dye transfer assays and with the syncytium formation assay. Two deacylation mutants lacking a CT or carrying serine residues substituting for Cys578 and Cys581 promoted full fusion. However, one of the single-acylation-site mutants, C6, in which Cys581 is replaced with serine, promoted hemifusion but not pore formation. In contrast, four other single-acylation-site mutants that have a sole cysteine residue in the CT at position 575, 577, 579, or 581 promoted full fusion. The impaired pore-forming ability of C6 was improved by amino acid substitution between residues 578 and 582 or by deletion of the carboxy-terminal leucine at position 582. Syncytium-forming ability, however, was not adequately restored by these mutations. These facts indicated that the acylation was not significant in membrane fusion by BHA but that pore formation and pore dilation were appreciably affected by the particular amino acid sequence of the CT and the existence of a single acylation site in CT residue 578.

Controlling Shrinkage in Wool Fabrics: Effective Hydrogen Peroxide Systems

Alkaline hydrogen peroxide (H2O2) systems, including dicyandiamide, gluconic acid, and Triton X surfactant, used alone or followed by enzyme treatments, are investigated for their effectiveness in imparting shrinkage resistance to wool fabrics. Fractional factorial analysis shows that H2O 2 is the most important factor and enzyme the second contributing factor in shrinkage control. An effective H2O2, nonenzymatic system with Triton X-114 limits structural changes to surface smoothing of the fibers and yields a relative area shrinkage of 2.95%. Another effective H2O2 system, using the same pretreatment but followed by an enzymatic treatment with additives—polyacrylamide to restrict enzyme activity to the fiber surface and sodium sulfite to reduce disulfide linkages—yields 1.16% area shrinkage. The most important factor in shrinkage control is replacing the hydro phobicity of the wool's surface with an anionic charge through the formation of cysteic acid. This leads to the release of 18-methyleicosanoic (18-MEA) acid from the fiber surface and underlying cell membrane complex attached to the surface scales of wool through thioester linkages. TLC, FTIR, and EI-MS are used to prove the presence of fatty acids and 18-MEA in spent baths and in extracts of the treated fabrics. Imparting hydrophilicity to wool by conferring an anionic charge suggests new possibilities for wool reactivity.

Palmitoylation of intracellular signaling proteins: regulation and function.

Protein S-palmitoylation is the thioester linkage of long-chain fatty acids to cysteine residues in proteins. Addition of palmitate to proteins facilitates their membrane interactions and trafficking, and it modulates protein-protein interactions and enzyme activity. The reversibility of palmitoylation makes it an attractive mechanism for regulating protein activity, and this feature has generated intensive investigation of this modification. The regulation of palmitoylation occurs through the actions of protein acyltransferases and protein acylthioesterases. Identification of the protein acyltransferases Erf2/Erf4 and Akr1 in yeast has provided new insight into the palmitoylation reaction. These molecules work in concert with thioesterases, such as acyl-protein thioesterase 1, to regulate the palmitoylation status of numerous signaling molecules, ultimately influencing their function. This review discusses the function and regulation of protein palmitoylation, focusing on intracellular proteins that participate in cell signaling or protein trafficking.

Molecular Characterization of Covalent Complexes between Tissue Transglutaminase and Gliadin Peptides

Tissue transglutaminase (TG2) modifies proteins and peptides by transamidation or deamidation of specific glutamine residues. TG2 also has a central role in the pathogenesis of celiac disease. The enzyme is both the target of disease-specific autoantibodies and generates deamidated gliadin peptides recognized by intestinal T cells from patients. Incubation of TG2 with gliadin peptides also results in the formation of covalent TG2-peptide complexes. Here we report the characterization of complexes between TG2 and two immunodominant gliadin peptides. Two types of covalent complexes were found; the peptides are either linked via a thioester bond to the active site cysteine of TG2 or via isopeptide bonds to particular lysine residues of the enzyme. We quantified the number of gliadin peptides bound to TG2 under different conditions. After 30 min of incubation of TG2 at 1 microm with an equimolar ratio of peptides to TG2, approximately equal amounts of peptides were bound by thioester and isopeptide linkage. At higher peptide to TG2 ratios, more than one peptide was linked to TG2, and isopeptide bond formation dominated. The lysine residues in TG2 that act as acyl acceptors were identified by matrix assisted laser desorption ionization and nanoelectrospray mass spectrometry and tandem mass spectrometry analysis of proteolytic digests of the TG2-peptide complexes. At a high molar excess of gliadin peptides to TG2 altogether six lysine residues of TG2 were found to participate in isopeptide bond formation. The results are relevant to the understanding of how antibodies to TG2 are formed in celiac disease.

Enzyme‐Catalyzed Preparation of Aliphatic Polyesters Containing Thioester Linkages

AbstractAliphatic polyesters containing thioester linkages were enzymatically prepared by both the copolymerization of lactone with mercaptoalkanoic acid and by the transesterification of polyesters with mercaptoalkanoic acids. The enzymatic copolymerization of ε‐caprolactone with 11‐mercaptoundecanoic acid (11MU) and 3‐mercaptopropionic acid (3MP) was performed under reduced pressure using an immobilized lipase from Candida antarctica (CA). The transesterification of poly(ε‐caprolactone) and poly[(R)‐3‐hydroxybutyrate] was carried out with 11MU and 3MP using lipase CA under reduced pressure. magnified image