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PubMed1984

Latencies and phosphomannosyl-enzyme receptors of lysosomal enzymes during the appearance and repair of exercise injuries in mouse skeletal muscles.

Latencies and phosphomannosyl-enzyme receptors of lysosomal enzymes were studied in the skeletal muscles of NMRI mice during the appearance (0-1 days) and the repair (3-9 days) of muscle fiber injuries after a single bout of prolonged running (9 hr, 13.5 m/min). The unsedimentable, releasable, and bound activities of arylsulfatase, beta-N-acetylglucosaminidase, beta-D-glucuronidase, cathepsin C, and ribonuclease as well as the content and occupancy of phosphomannosyl-enzyme receptors of lysosomal enzymes were assayed. The distribution of enzyme activities in different fractions as well as the changes after exertion greatly varied between different lysosomal enzymes. In general, the total activities and also the distribution of enzyme activities in different fractions were unaffected 1 hr after exertion, but on the day after exertion small increases were observed in the free and releasable activities. The highest enzyme activities both in the homogenate and in different fractions were recorded 3 days after exertion, after which the activities slowly decreased. The increases of enzyme activities were higher in the free and releasable fractions than in the homogenate but the changes in the proportional distributions of lysosomal enzyme activities between different fractions were minor. The present study also showed the presence of phosphomannosyl-enzyme receptors of lysosomal enzymes in the membranes of skeletal muscles. The total content of phosphomannosyl-enzyme receptors was unchanged 0-3 days after exertion but a small increase occurred 5-8 days after exertion. Instead, the occupancy of these lysosomal receptors with endogenous enzymes was significantly increased 1-5 days after exertion and decreased later to the control level.

Acetylglucosaminidase↗
PubMed1988

Prolyl 4-hydroxylase from Volvox carteri. A low-Mr enzyme antigenically related to the alpha subunit of the vertebrate enzyme.

Prolyl 4-hydroxylase was isolated in a highly purified form from a multi-cellular green alga, Volvox carteri, by a procedure consisting of ion-exchange chromatography and affinity chromatography on poly(L-hydroxyproline) coupled to Sepharose. Two other affinity-column procedures were also developed, one involving 3,4-dihydroxyphenylacetate and the other 3,4-dihydroxyphenylpropionate linked to Sepharose. The Km values of the Volvox enzyme for the co-substrates and the peptide substrate, as well as the inhibition constants for selected 2-oxoglutarate analogues, were similar to those of the enzyme from Chlamydomonas reinhardii, except that the Km for 2-oxoglutarate with the Volvox enzyme was 6-fold greater. The temperature optimum of the Volvox enzyme was also 10 degrees C higher. The apparent Mr of the Volvox enzyme by gel filtration was about 40,000, being similar to that reported for the Chlamydomonas enzyme but markedly lower than that of the vertebrate enzymes. A similar apparent Mr of about 40,000 was also found for prolyl 4-hydroxylase from the green alga Enteromorpha intestinalis, whereas the enzyme from various vascular plants gave an apparent Mr greater than 300,000. SDS/polyacrylamide-gel electrophoresis demonstrated in the highly purified Volvox enzyme the presence of a major protein band doublet with a Mr of about 65,000 and a minor doublet of Mr about 55,000-57,000. A polyclonal antiserum, prepared against the Mr-65,000 doublet, stained in immunoblotting the Mr-65,000 doublet as well as the alpha subunit, but not the beta subunit, of the vertebrate prolyl 4-hydroxylase. An antiserum against the beta subunit of the vertebrate enzyme stained in immunoblotting a Mr-50,000 polypeptide in a partially purified Volvox enzyme preparation, but did not stain either the Mr-65,000 or the Mr-55,000-57,000 doublet of the highly purified enzyme. The data thus suggest that the active Volvox carteri prolyl 4-hydroxylase is an enzyme monomer antigenically related to the alpha subunit of the vertebrate enzyme.

Chlorophyta↗
PubMed1988

Regulation of enzyme levels in the blood. Influence of environmental and genetic factors on enzyme clearance.

Since its discovery, lactic dehydrogenase virus (LDV) has remained unique as a model of long-term enzyme elevation due to impairment of enzyme clearance. The present study shows that mice inoculated with silica develop an increase in plasma lactate dehydrogenase (LDH) lasting for at least 6 months and that the enzyme elevation is due, at least in part, to impairment of clearance. The extent of the enzyme elevation is dependent on both the dose and route of silica administration and mice that had received both silica and LDV showed a more profound impairment of LDH clearance than mice that had received silica or LDV alone. Examination of the factors that regulate circulating enzyme levels in normal mice revealed that whereas there was no difference in resting enzyme levels among several inbred strains of mice (BALB/cAnN, NZBWF1/J,B10.D2/nSnN, and A/J mice), when mice were stressed by the administration of an enzyme load, certain inbred strains (BALB/cAnN) cleared the enzyme rapidly and others (B10.D2/nSnN) cleared the enzyme slowly. Moreover, in B10.D2/nSnN mice, enzyme clearance was age-related. When different strains of mice were infected with LDV, LDH levels were substantially higher in the circulation of slow enzyme clearers as compared to rapid enzyme clearers. It is concluded that both environmental and genetic factors influence the clearance of LDH and that impairment of enzyme clearance may be a more important factor than previously suspected in regulating enzyme levels in disease states.

Animals↗
PubMed1988

The molecular basis for a cytosolic malic enzyme null mutation. Malic enzyme mRNA from MOD-1 null mice contains an internal in-frame duplication that extends the coding sequence by 522 nucleotides.

Many tissues from wild type mice express cytosolic malic enzyme activity and contain two mRNAs (2.0 and 3.1 kilobases (kb)) that encode a single 64-kDa malic enzyme subunit polypeptide. MOD-1 null mutant mice lack cytosolic malic enzyme activity but express 2.5- and 3.6-kb mRNAs that hybridize with wild type malic enzyme cDNAs and are induced in liver by a starvation/carbohydrate refeeding regimen. To investigate the basis of the MOD-1 null mutation, a lambda gt11 cDNA library was constructed using mRNA from the livers of induced MOD-1 null mice as a template. A recombinant phage with a 2-kb insert was isolated by screening with wild type malic enzyme cDNA probes. The subcloned insert exhibited an atypical (non-wild type) restriction pattern and was subjected to sequence analysis. MOD-1 null malic enzyme cDNA contains an internal tandemly duplicated sequence that corresponds to nucleotides 1027-1548 in the coding region of wild type murine malic enzyme cDNA (Bagchi, S., Wise, L. S., Brown, M. L., Bregman, D., Sul, H. S., and Rubin, C. S. (1987) J. Biol. Chem. 262, 1558-1565). An open reading frame is retained throughout the duplicated sequence. The discovery of a 522-nucleotide in-frame duplication accounts for the increased size of MOD-1 null malic enzyme mRNAs and suggests that a variant malic enzyme polypeptide that is 19 kDa larger than the wild type subunit might be found in mutant mice. Western immunoblot analysis disclosed that MOD-1 null liver cytosol contains an 82-kDa protein that is recognized by anti-malic enzyme antibodies. Under stringent conditions, an anti-sense 32P-oligonucleotide that spans the abnormal junction between the reiterated sequences hybridized with the 2.5 and 3.6-kb MOD-1 null malic enzyme mRNAs but failed to form stable complexes with wild type malic enzyme mRNAs. Thus, both MOD-1 null malic enzyme mRNAs contain the duplication deduced from cDNA sequence analyses. The MOD-1 null mutation might originate from an unequal crossover between homologous regions of two different introns in the malic enzyme gene, thereby causing the duplication of one or more exons.

Animals↗
PubMed1998

Identification of the human P-450 enzymes responsible for the sulfoxidation and thiono-oxidation of diethyldithiocarbamate methyl ester: role of P-450 enzymes in disulfiram bioactivation.

Diethyldithiocarbamate methyl ester (DDTC-Me) is a precursorto the formation of S-methyl-N,N-diethylthiolcarbamate sulfoxide, the active metabolite proposed to be responsible for the alcohol deterrent effects of disulfiram. The present study investigated the role of human cytochrome P-450 (CYP) enzymes in sulfoxidation and thiono-oxidation of DDTC-Me, intermediary steps in the activation of disulfiram. Several approaches were used in an attempt to delineate the particular P-450 enzyme(s) involved in the sulfoxidation and thiono-oxidation of DDTC-Me. These approaches included the use of cDNA-expressed human P-450 enzymes, correlation analysis with sample-to-sample variation in human P-450 enzymes in a bank of human liver microsomes, and chemical and antibody inhibition studies. Multiple human P-450 enzymes (CYP3A4, CYP1A2, CYP2A6, and CYP2D6) catalyzed the sulfoxidation of DDTC-Me, as determined with cDNA-expressed enzymes. Several lines of evidence suggest that the sulfoxidation of DDTC-Me by human liver microsomes is primarily catalyzed by CYP3A4/5, including (1) a high correlation between DDTC-Me sulfoxidation and testosterone 6beta-hydroxylation; (2) increased DDTC-Me sulfoxidation in the presence of alpha-naphthoflavone, an activator of CYP3A enzymes; (3) inhibition of this reaction by inhibitors of CYP3A4/5 enzymes, such as troleandomycin and ketoconazole; and (4) inhibition of DDTC-Me sulfoxidation by antibodies against CYP3A enzymes. On the other hand, several lines of evidence suggested that the thiono-oxidation of DDTC-Me by human liver microsomes is catalyzed in part by CYP1A2, CYP2B6, CYP2E1, and CYP3A4/5, including (1) these human P450 enzymes among others have the capacity to catalyze this reaction, as determined with cDNA-expressed enzymes; (2) a high correlation between DDTC-Me thiono-oxidation and testosterone 6beta-hydroxylation, weak inhibition by ketoconazole, troleandomycin, and anti-CYP3A antibodies suggested a minor role for CYP3A4; (3) a high correlation with immunoreactive CYP2B6 suggested involvement of this enzyme; (4) weak inhibition of DDTC-Me thiono-oxidation by furafylline and anti-CYP1A antibody suggested involvement of CYP1A2; and (5) inhibition of DDTC-Me thiono-oxidation by DDTC and anti-CYP2E antibodies suggested a role for CYP2E1. Collectively, these data suggested CYP3A4/5 enzymes are the major contributors to the sulfoxidation of DDTC-Me by human liver microsomes, and CYP1A2, CYP2B6, CYP2E1, and CYP3A4/5 contribute toward DDTC-Me thiono-oxidation by human liver microsomes. This study, in conjunction with others (Madan et al., Drug Metab. Dispos. 23:1153-1162, 1995), may help explain the variability in disulfiram's effectiveness as an alcohol deterrent.

Alcohol Deterrents↗
PubMed2001

Development of a multipurpose feed enzyme analyzer to estimate and evaluate the profitability of using feed enzyme preparations for poultry.

Previous studies have demonstrated that a log-linear equation could accurately predict chick performance when a feed enzyme was added to a diet and that the slope of the equation provided a measure of the efficacy of different enzymes. The objective of the study was to develop a software package, a Multipurpose Feed Enzyme Analyzer (MPFEA), based on an equation designed to evaluate the profitability of using feed enzymes. A high correlation between the efficacy of different feed enzymes (B values, the slopes of the equations) and the maximal profits was obtained when feed enzymes were added to a barley-based diet (r2 = 0.99, P < 0.0005). In contrast, there was a low correlation between the B values and the maximal profits when a feed enzyme was added to different cereal-based diets (r2 = 0.61, P = 0.2171). It appeared that there is not always a close association between efficacy of an enzyme when added to different cereal-based diets and the corresponding profitability. The MPFEA was highly versatile, as any combination of inputs such as the amounts of a feed enzyme and a substituted cereal required to yield a profit level could be determined. In conclusion, the MPFEA can accurately evaluate profitability of using different feed enzymes; select the most profitable cereal for a given feed enzyme; determine the optimal amounts of a feed enzyme, a cereal, or both; and even estimate the alternate price for a feed enzyme and a cereal. It should provide a useful tool for nutritionists.

Animal Feed↗
PubMed1976

[Distribution of intravenously injected enzymes of heterologous, homologous and autologous origin. Distribution and transport of cell enzymes within the extracellular space. III (author's transl)].

The disappearance rates of intravenously injected enzymes of heterologous, homologous and autologous origin were determined in rats. Within four hours after administration, the activities show an exponential decline, that is either mono- or biphasic. The constant of the exponential function is a measure of the capillary permeability. In the case of biphasic disappearance this holds true only for the first slope, whereas the second one represents the elimination of active enzyme molecules from the extracellular space. If the decline in enzyme activity is monophasic the elimination of those enzymes from the interstitial space is limited by the permeability of the capillary membrane. Enzymes of homologous and autologous origin (extracts of liver or muscle) show a close correlation between their molecular weights and their rates of distribution within the extracellular compartment. For heterologous enzymes (crystallized) such a correlation could not be found. Possible causes for these differences in distribution are discussed. Heterologous and/or crystallized enzymes seem not to be suited for studies on the distribution of cell enzymes within the extracellular space. After enzymes are released from injured cells they undergo the processes of distribution, transport and elimination which are superimposed. The effects of the distribution and transport of enzymes on the results of clinical studies on enzyme elimination are discussed. It seems questionable at this point to assume that from the elimination rate of enzymes and their actual plasma activity one can account for the amount of enzymes originally released from injured cells.

Animals↗
PubMed1989

Quinoprotein D-glucose dehydrogenases in Acinetobacter calcoaceticus LMD 79.41: purification and characterization of the membrane-bound enzyme distinct from the soluble enzyme.

Acinetobacter calcoaceticus is known to contain soluble and membrane-bound quinoprotein D-glucose dehydrogenases while other oxidative bacteria such as Pseudomonas or Gluconobacter contain only membrane-bound enzyme. The two different forms were believed to be the same enzyme or interconvertible. Present results show that the two different forms of glucose dehydrogenase are distinct from each other in their enzymatic and immunological properties as well as in their molecular size. The soluble and membrane-bound glucose dehydrogenases were separated after French press-disruption by repeated ultracentrifugation, and then purified to nearly homogeneous state. The soluble enzyme was a polypeptide of 55 Kdaltons, while the membrane-bound enzyme was a polypeptide of 83 Kdaltons which is mainly monomeric in detergent solution. Both enzymes showed different enzymatic properties including substrate specificity, optimum pH, kinetics for glucose, and reactivity for ubiquinone-homologues. Furthermore, the two enzymes could be distinguished immunochemically; the membrane-bound enzyme is cross-reactive with an antibody raised against membrane-bound enzyme purified from Pseudomonas but not with antibody elicited against the soluble enzyme, while the soluble enzyme is not cross-reactive with the antibody of membrane-bound enzyme. Data also suggest that the membrane-bound enzyme functions by linking to the respiratory chain via ubiquinone though the function of the soluble enzyme remains unclear.

Acinetobacter↗
PubMed1978

Studies on regulatory functions of malic enzymes. V. Comparative studies of malic enzymes in bacteria.

Screening of four malic enzymes--NAD-linked enzyme [EC 1.1.1.38], NAD, NADP-linked enzyme [EC 1.1.1.39], NADP-linked enzyme [EC 1.1.1.40], and D-malic enzyme--was carried out with cell-free extracts of the following 16 strains of bacteria by the aid of Sepharose 6B column chromatography: 9 strains of enteric bacteria, 3 strains of Pseudomonas, Alcaligenes faecalis, Agrobacterium tumefaciens, Rhodospirillum rubrum, and Clostridium tetanomorphum. All the strains tested contained at least one malic enzyme. The NADP-linked enzyme activity was found in all the strains except C. tetanomorphum, the NAD-linked enzyme activity in 12 strains--8 strains of enteric bacteria, 2 strains of Pseudomonas, Ag. tumefaciens, and C. tetanomorphum--and D-malic enzyme activity in 4 strains--A, aerogenes (IFO 3319 and 12059), Ps. fluorescens, and R. rubrum. The NADP-linked and NAD-linked enzyme activities of two strains of Pseudomonas were not separated by the chromatography. The available evidence suggested that the NAD, NADP-linked enzyme was not present in these 16 strains. The comparative studies of molecular, enzymatic, and serological properties of the malic enzymes in these 16 strains revealed a close similarity of the same types of malic enzymes among enteric bacteria.

Alcaligenes↗
PubMed1993

Structural and functional properties of a multi-enzyme complex from spinach chloroplasts. 2. Modulation of the kinetic properties of enzymes in the aggregated state.

The carboxylase activity of free ribulose 1,5-bisphosphate carboxylase-oxygenase has been compared to that of the five-enzyme complex present in chloroplasts. Kinetic results have shown that the V/active site is lower for the free enzyme than for the complex. Conversely the Km is smaller for the complex than for the free enzyme. This implies that the catalytic activity of the enzyme is enhanced when it is embedded in the complex. Under reducing conditions and in the presence of reduced thioredoxin, inactive oxidized phosphoribulokinase, free in solution or inserted in the multi-enzyme complex, becomes active. The kinetics of this activation process has been studied and shown to be exponential. The time constant of this exponential decreases, for the free enzyme, as thioredoxin concentration is increased. Alternatively, for the enzyme embedded in the complex, this time constant increases with thioredoxin concentration almost in a linear fashion. This implies that the complex is much more rapidly activated by reduced thioredoxin than is the free phosphoribulokinase. The variation of the amplitude of this activation process as a function of thioredoxin concentration is a hyperbola. The concentration of thioredoxin which results in half the asymptotic value of this hyperbola is smaller for the complex than for the free enzyme. A kinetic model has been proposed and the dynamic equations resulting from this model have been derived. They fit the experimental results exactly. From the variation of the amplitude of the activation process one may derive the binding constants of thioredoxin on either the oxidized enzyme or on a partly dithiothreitol-reduced enzyme (both of them free or inserted in the complex). In either case, the affinity of reduced thioredoxin is larger for the complex than for the free enzyme. The individual values of some of the rate constants have also been estimated from the variation of the time constants as a function of thioredoxin concentration. Taken together, these results show that at least two enzymes, ribulose 1,5-bisphosphate carboxylase-oxygenase and phosphoribulokinase, have quite different kinetic properties depending on whether they are in free solution or embedded in the multi-enzyme complex.

Chloroplasts↗
PubMed2000

Angiotensin converting enzyme inhibitors in normotensive diabetic patients with microalbuminuria.

OBJECTIVES: To examine whether the progression of early diabetic renal disease to end-stage renal failure may be slowed by the use of angiotensin converting enzyme inhibitors for reasons other than their antihypertensive properties, so that they have value in the treatment of normotensive diabetics with microalbuminuria. SEARCH STRATEGY: MEDLINE was searched for English language reviews and randomised controlled trials. Personal reference lists, and reference lists of retrieved studies were also used. SELECTION CRITERIA: Randomised controlled trials with separate identifiable results for initially normotensive diabetic patients, who received angiotensin converting enzyme inhibitors for at least one year and were compared with controls. DATA COLLECTION AND ANALYSIS: Meta-analyses were performed on the results of 11 randomised controlled trials with a variety of patient inclusion and exclusion criteria. MAIN RESULTS: Albumin excretion rate fell for patients on angiotensin converting enzyme inhibition in 10 of the 11 studies but did so for only two of the 11 groups on placebo. Treatment provided a significant reduction in albumin excretion rate in both insulin dependent diabetes mellitus and non insulin dependent diabetes mellitus. Treatment with either captopril, enalapril or lisinopril reduced albumin excretion rate in comparison with control patients. A greater lowering of blood pressure was experienced by initially normotensive patients in the angiotensin converting enzyme inhibitor than in the placebo group. Pooled end-of-study mean blood pressures for the treated group were significantly lower than for the untreated group, although this was not so for all individual studies. The apparent (treatment - placebo) 'effect' on systolic and diastolic pressures had a larger standard error for longer lasting studies. Average haemoglobin fell a little in the treated patients and rose in the controls but neither this nor the difference in changes in glomerular filtration rate reached statistical significance. REVIEWER'S CONCLUSIONS: Inhibition of angiotensin converting enzyme can arrest or reduce the albumin excretion rate in microalbuminuric normotensive diabetics, as well as reduce or prevent an increase in blood pressure. But, given the drop in blood pressure in patients on angiotensin converting enzyme inhibitors, it is not possible to be certain that the reduction of albumin excretion rate is due to a separate renal effect. A direct link with postponement of end-stage renal failure has not been demonstrated. There appear to be no substantial side effects.

Albuminuria↗
PubMed1979

The constant proportion enzyme group concept in the selection of reference enzymes in metabolism.

Comparative analyses of enzyme activity patterns reveal groups of enzymes with constant proportions and enzymes with variable proportions of their maximum activities. Constant proportion groups comprise enzymes of unbranched metabolic sequences or functionally related pathways. Ratios of constant proportion groups reflect metabolic correlations, which may be used as discriminative magnitudes of metabolic specialization. Comparison of closely related muscles reveals that differences in the absolute levels of the constant proportion group enzymes of glycolysis parallel differences in maximum glycolytic flux rates. This holds for near-equilibrium as well as for non-equilibrium enzymes. In any case, maximum enzyme activities are significantly higher than maximum metabolic flux rates. Maximum enzyme activities therefore do not permit conclusions on maximum metabolic capacities to be drawn. They may, however, be compared in closely related tissues or different metabolic conditions of a given tissue as relative magnitudes of maximum flux rates. Reference enzymes of constant proportion groups as well as of other enzymes which are representative of distinct metabolic pathways may be used in this sense for the evaluation of enzyme activity patterns. Selection of appropriate enzymes depends on the aim of the intended study, on a thorough knowledge of their individual properties, and on the possibility of measuring their maximum activity under reproducible conditions.

Animals↗
PubMed1981

Angiotensin converting enzyme in cultured endothelial cells and growth medium. Relationships to enzyme from kidney and plasma.

We have previously reported that cultured cells from swine aorta possess angiotensin converting enzyme (peptidyldipeptide hydrolase, EC 3.4.15.1) and release it into serum-free culture medium. The present work compares enzyme from these two sources, and from swine kidney and serum, with respect to antibody and lectin binding. Purified enzyme from swine kidney, and the activity in swine serum, cultured endothelial cells and culture medium bind similarly to rabbit antibodies prepared against the kidney converting enzyme. Enzyme from each of these sources was allowed to bind to an immobilized lectin (Ricinus communis), which binds to terminal galactose residues of glycoproteins. Increasing concentrations of galactose were used to remove enzyme from the lectin column and the distribution of enzyme activity in the galactose eluates was determined. The elution pattern was similar for kidney and endothelial cell enzyme, and different from the pattern found for both serum and medium enzymes. Neuraminidase treatment of either serum or medium enzyme altered the distribution of activity eluted to that found for endothelial cell or kidney enzymes. The effects of neuraminidase suggest that the difference in lectin binding between cell and medium enzyme reflects differences in the number of terminal sialic acid residues that cover galactose residues.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2004

Immobilization of the enzyme beta-lactamase on biotin-derivatized poly(L-lysine)-g-poly(ethylene glycol)-coated sensor chips: a study on oriented attachment and surface activity by enzyme kinetics and in situ optical sensing.

Understanding the conformation, orientation, and specific activity of proteins bound to surfaces is crucial for the development and optimization of highly specific and sensitive biosensors. In this study, the very efficient enzyme beta-lactamase is used as a model protein. The wild-type form was genetically engineered by site-directed mutagenesis to introduce single cysteine residues on the surface of the enzyme. The cysteine thiol group is subsequently biotinylated with a dithiothreitol (DTT)-cleavable biotinylation reagent. beta-Lactamase is then immobilized site-specifically via the biotin group on neutral avidin-covered surfaces with the aim to control the orientation of the enzyme molecule at the surface and study its effect on enzymatic activity using Nitrocefin as the substrate. The DTT-cleavable spacer allows the release of the specifically bound enzyme from the surface. Immobilization of the enzyme is performed on a monolayer of the polycationic, biotinylated polymer PLL-g-PEG/PEG-biotin assembled on niobium oxide (Nb2O5) surfaces via neutral avidin as the docking site. Two different assembly protocols, the sequential adsorption of avidin and biotinylated beta-lactamase and the immobilization of preformed complexes of beta-lactamase and avidin, are compared in terms of immobilization efficiency. In situ optical waveguide lightmode spectroscopy and colorimetric analysis of enzymatic activity were used to distinguish between specific and unspecific enzyme adsorption, to sense quantitatively the amount of immobilized enzyme, and to determine Michaelis-Menten kinetics. All tested enzyme variants turned out to be active upon immobilization at the polymeric surface. However, the efficiency of immobilized enzymes relative to the soluble enzymes was reduced about sevenfold, mainly because of impaired substrate (Nitrocefin) diffusion or restricted accessibility of the active site. No significant effect of different enzyme orientations could be detected, probably because the enzymes were attached to the surface through long, flexible PEG chain linkers.

Adsorption↗