Monitoring galactolipid digestion and simultaneous changes in lipid-bile salt micellar organization by real-time NMR spectroscopy.

The use of Nuclear Magnetic Resonance spectroscopy for studying lipid digestion in vitro most often consists of quantifying lipolysis products after they have been extracted from the reaction medium using organic solvents. However, the current sensitivity level of NMR spectrometers makes possible to avoid the extraction step and continuously quantify the lipids directly in the reaction medium. We used real-time 1H NMR spectroscopy and guinea pig pancreatic lipase-related protein 2 (GPLRP2) as biocatalyst to monitor in situ the lipolysis of monogalactosyl diacylglycerol (MGDG) in the form of mixed micelles with the bile salt sodium taurodeoxycholate (NaTDC). Residual substrate and lipolysis products (monogalactosyl monoacylglycerol (MGMG); monogalactosylglycerol (MGG) and octanoic acid (OA) were simultaneously quantified throughout the reaction thanks to specific proton resonances. Lipolysis was complete with the release of all MGDG fatty acids. These results were confirmed by thin layer chromatography (TLC) and densitometry after lipid extraction at different reaction times. Using diffusion-ordered NMR spectroscopy (DOSY), we could also estimate the diffusion coefficients of all the reaction compounds and deduce the hydrodynamic radius of the lipid aggregates in which they were present. It was shown that MGDG-NaTDC mixed micelles with an initial hydrodynamic radius rH of 7.3 ± 0.5 nm were changed into smaller micelles of NaTDC-MGDG-MGMG of 2.3 ± 0.5 nm in the course of the lipolysis reaction, and finally into NaTDC-OA mixed micelles (rH of 2.9 ± 0.5 nm) and water soluble MGG. These results provide a better understanding of the digestion of galactolipids by PLRP2, a process that leads to the complete micellar solubilisation of their fatty acids and renders their intestinal absorption possible.

Location of the photosynthetic carbon metabolism in microcompartments and separated phases in microalgal cells.

Carbon acquisition, assimilation and storage in eukaryotic microalgae and cyanobacteria occur in multiple compartments that have been characterised by the location of the enzymes involved in these functions. These compartments can be delimited by bilayer membranes, such as the chloroplast, the lumen, the peroxisome, the mitochondria or monolayer membranes, such as lipid droplets or plastoglobules. They can also originate from liquid-liquid phase separation such as the pyrenoid. Multiple exchanges exist between the intracellular microcompartments, and these are reviewed for the CO2 concentration mechanism, the Calvin-Benson-Bassham cycle, the lipid metabolism and the cellular energetic balance. Progress in microscopy and spectroscopic methods opens new perspectives to characterise the molecular consequences of the location of the proteins involved, including intrinsically disordered proteins.

Pre-duodenal lipid digestion of emulsions: Relevance, colloidal aspects and mechanistic insight.

The digestion of lipids in the human body has several health and nutritional implications. Lipid digestion is an interfacial phenomenon meaning that water-soluble lipases need to first adsorb to the oil-water interface before enzymatic conversions can start. The digestion of lipids mainly occurs on colloidal structures dispersed in water, such as oil-in-water (o/w) emulsions, which can be designed during food formulation/processing or structured during digestion. From a food design perspective, different in vitro studies have demonstrated that the kinetics of lipid digestion can be influenced by emulsion properties. However, most of these studies have been performed with pancreatic enzymes to simulate lipolysis in the small intestine. Only few studies have dealt with lipid digestion in the gastric phase and its subsequent impact on intestinal lipolysis. In this aspect, this review compiles information on the physiological aspects of gastric lipid digestion. In addition, it deals with colloidal and interfacial aspects starting from emulsion design factors and how they evolve during in vitro digestion. Finally, molecular mechanisms describing gastric lipolysis are discussed.

Interfacial adsorption and activity of pancreatic lipase-related protein 2 onto heterogeneous plant lipid model membranes.

Pancreatic lipase related-protein 2 (PLRP2) exhibits remarkable galactolipase and phospholipase A1 activities, which depend greatly on the supramolecular organization of the substrates and the presence of surfactant molecules such as bile salts. The objective of the study was to understand the modulation of the adsorption mechanisms and enzymatic activity of Guinea pig PLRP2 (gPLRP2), by the physical environment of the enzyme and the physical state of its substrate. Langmuir monolayers were used to reproduce homogeneous and heterogeneous photosynthetic model membranes containing galactolipids (GL), and/or phospholipids (PL), and/or phytosterols (pS), presenting uncharged or charged interfaces. The same lipid mixtures were also used to form micrometric liposomes, and their gPLRP2 catalyzed digestion kinetics were investigated in presence or in absence of bile salts (NaTDC) during static in vitro, so called "bulk", digestion. The enzymatic activity of gPLRP2 onto the galactolipid-based monolayers was characterized with an optimum activity at 15 mN/m, in the absence of bile salts. gPLRP2 showed enhanced adsorption onto biomimetic model monolayer containing negatively charged lipids. However, the compositional complexity in the heterogeneous uncharged model systems induced a lag phase before the initiation of lipolysis. In bulk, no enzymatic activity could be demonstrated on GL-based liposomes in the absence of bile salts, probably due to the high lateral pressure of the lipid bilayers. In the presence of NaTDC (4 mM), however, gPLRP2 showed both high galactolipase and moderate phospholipase A1 activities on liposomes, probably due to a decrease in packing and lateral pressure upon NaTDC adsorption, and subsequent disruption of liposomes.

In situ monitoring of galactolipid digestion by infrared spectroscopy in both model micelles and spinach chloroplasts.

Galactolipids are the main lipids from plant photosynthetic membranes and they can be digested by pancreatic lipase related protein 2 (PLRP2), an enzyme found in the pancreatic secretion in many animal species. Here, we used transmission Fourier-transform infrared spectroscopy (FTIR) to monitor continuously the hydrolysis of galactolipids by PLRP2, in situ and in real time. The method was first developed with a model substrate, a synthetic monogalactosyl diacylglycerol with 8-carbon acyl chains (C8-MGDG), in the form of mixed micelles with a bile salt, sodium taurodeoxycholate (NaTDC). The concentrations of the residual substrate and reaction products (monogalactosylmonoglyceride, MGMG; monogalactosylglycerol, MGG; octanoic acid) were estimated from the carbonyl and carboxylate vibration bands after calibration with reference standards. The results were confirmed by thin layer chromatography analysis (TLC) and specific staining of galactosylated compounds with thymol and sulfuric acid. The method was then applied to the lipolysis of more complex substrates, a natural extract of MGDG with long acyl chains, micellized with NaTDC, and intact chloroplasts isolated from spinach leaves. After a calibration performed with α-linolenic acid, the main fatty acid (FA) found in plant galactolipids, FTIR allowed quantitative measurement of chloroplast lipolysis by PLRP2. A full release of FA from membrane galactolipids was observed, that was not dependent on the presence of bile salts. Nevertheless, the evolution of amide vibration band in FTIR spectra suggested the interaction of membrane proteins with NaTDC and lipolysis products.

Digestibility and oxidative stability of plant lipid assemblies: An underexplored source of potentially bioactive surfactants?

Most lipids in our diet come under the form of triacylglycerols that are often redispersed and stabilized by surfactants in processed foods. In plant however, lipid assemblies constitute interesting sources of natural bioactive and functional ingredients. In most photosynthetic sources, polar lipids rich in ω3 fatty acids are concentrated. The objective of this review is to summarize all the knowledge about the physico-chemical composition, digestive behavior and oxidative stability of plant polar lipid assemblies to emphasize their potential as functional ingredients in human diet and their potentialities to substitute artificial surfactants/antioxidants. The specific composition of plant membrane assemblies is detailed, including plasma membranes, oil bodies, and chloroplast; emphasizing its concentration in phospholipids, galactolipids, peculiar proteins, and phenolic compounds. These molecular species are hydrolyzed by specific digestive enzymes in the human gastrointestinal tract and reduced the hydrolysis of triacylglycerols and their subsequent absorption. Galactolipids specifically can activate ileal break and intrinsically present an antioxidant (AO) activity and metal chelating activity. In addition, their natural association with phenolic compounds and their physical state (Lα state of digalactosyldiacylglycerols) in membrane assemblies can enhance their stability to oxidation. All these elements make plant membrane molecules and assemblies very promising components with a wide range of potential applications to vectorize ω3 polyunsaturated fatty acids, and equilibrate human diet.

Modulation of gastric lipase adsorption onto mixed galactolipid-phospholipid films by addition of phytosterols.

The rapid and preferential adsorption of a gastric lipase recombinant dog gastric lipase (rDGL) in heterogeneous films of phospholipids and triacylglycerols has previously been unveiled using Langmuir films analyzed by tensiometry, ellipsometry and Langmuir-Blodgett transfer coupled to atomic force microscopy. Here we invest the adsorption behavior of rDGL in heterogeneous galactolipid and mixed galactolipid-phospholipid or galactolipid-phospholipid-phytosterol films representative of plant membrane. Again rDGL, preferentially got adsorbed at the expanded lipid phases of the films underlining the genericity of such adsorption behavior. The addition of phytosterols to these mixtures resulted in the creation of defects, favoring the adsorption of rDGL at the fluid phases, but also improving the adsorption capacities of the lipase at the phase boundaries and towards the defects in the condensed phase. rDGL, like all gastric lipases, does not show any activity on galactolipids and phospholipids but its adsorption impacts their lateral organization and may change the adsorption and activity of other lipolytic enzymes in the course of digestion.

A Trajectory of Discovery: Metabolic Regulation by the Conditionally Disordered Chloroplast Protein, CP12.

The chloroplast protein CP12, which is widespread in photosynthetic organisms, belongs to the intrinsically disordered proteins family. This small protein (80 amino acid residues long) presents a bias in its composition; it is enriched in charged amino acids, has a small number of hydrophobic residues, and has a high proportion of disorder-promoting residues. More precisely, CP12 is a conditionally disordered proteins (CDP) dependent upon the redox state of its four cysteine residues. During the day, reducing conditions prevail in the chloroplast, and CP12 is fully disordered. Under oxidizing conditions (night), its cysteine residues form two disulfide bridges that confer some stability to some structural elements. Like many CDPs, CP12 plays key roles, and its redox-dependent conditional disorder is important for the main function of CP12: the dark/light regulation of the Calvin-Benson-Bassham (CBB) cycle responsible for CO2 assimilation. Oxidized CP12 binds to glyceraldehyde-3-phosphate dehydrogenase and phosphoribulokinase and thereby inhibits their activity. However, recent studies reveal that CP12 may have other functions beyond the CBB cycle regulation. In this review, we report the discovery of this protein, its features as a disordered protein, and the many functions this small protein can have.

Interfacial organization and phase behavior of mixed galactolipid-DPPC-phytosterol assemblies at the air-water interface and in hydrated mesophases.

The structural behavior of model assemblies composed of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), the two main galactolipids found in plants, was investigated at the air/water interface and in aqueous dispersion. To approach the composition of the natural photosynthetic membranes, tunable Langmuir model membrane of galactolipids (GL) were used, and were complexified to form either heterogenous binary or ternary assemblies of GL, phospholipids (PL), and phytosterols (pS). The impact of pS, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or both on the structural properties of GL membrane was studied. The nature of the interactions between the different molecules was investigated using biophysical characterizations (ellipsometry, tensiometry, atomic force microscopy). In addition, the phase behavior was determined by SAXS analysis on the model assemblies in aqueous dispersions. Results revealed the good interfacial stability of these specific plant membrane lipids. The morphology of the GL film was characteristic of a fluid phase, with an interfacial roughness induced by the intercalation of monogalactosyl and digalactosyl polar heads of MGDG and DGDG, respectively. A phase heterogeneity in the monolayer was induced by the addition of DPPC and/or pS, which resulted in the modification of galactolipid organization and headgroup interactions. These structural changes were confirmed by SAXS analysis, showing more favorable interactions between MGDG and DPPC than between DGDG and DPPC in aqueous dispersion. This phenomenon was exacerbated in the presence of pS.

Bioaccessibility of essential lipophilic nutrients in a chloroplast-rich fraction (CRF) from agricultural green waste during simulated human gastrointestinal tract digestion.

An in vitro gastrointestinal human digestion model, with and without additional rapeseed oil, was used to measure the bioaccessibility of the major lipophilic nutrients enriched in chloroplasts: ß-carotene; lutein; α-tocopherol; and α-linolenic acid. Chloroplast-rich fraction (CRF) material for this work was prepared from post-harvest pea vine field residue (pea vine haulm, or PVH), an abundant source of freely available, underutilised green biomass. PVH was either steam sterilised (100 °C for 4 min) and then juiced (heat-treated PVH, or HPVH), or was juiced fresh and the juice heated (90 °C for 3 min) (heat-treated juice, or HJ); the CRF from all biomass treatments was recovered from the juice by centrifugation. The impact of postharvest heat treatment of the biomass (HPVH), or of heat treatment of the juice (HJ) derived from the biomass, on the retention and bioaccessibility of the target nutrients was determined. The results showed that both heat treatments increased the apparent retention of ß-carotene, lutein, α-tocopherol, and α-linolenic acid in the CRF material during digestion. The presence of edible oil during digestion did not dramatically affect the retention of these nutrients, but it did increase the bioaccessibility of ß-carotene, lutein, and α-tocopherol from CRF material derived from heated biomass or juice. The presence of oil also increased the bioaccessibility of ß-carotene, but not of lutein, α-tocopherol, or α-linolenic acid, from fresh CRF material.

Reduction in Phosphoribulokinase Amount and Re-Routing Metabolism in Chlamydomonas reinhardtii CP12 Mutants.

The chloroplast protein CP12 is involved in the dark/light regulation of the Calvin-Benson-Bassham cycle, in particular, in the dark inhibition of two enzymes: glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK), but other functions related to stress have been proposed. We knocked out the unique CP12 gene to prevent its expression in Chlamydomonas reinhardtii (ΔCP12). The growth rates of both wild-type and ΔCP12 cells were nearly identical, as was the GAPDH protein abundance and activity in both cell lines. On the contrary, the abundance of PRK and its specific activity were significantly reduced in ΔCP12, as revealed by relative quantitative proteomics. Isolated PRK lost irreversibly its activity over-time in vitro, which was prevented in the presence of recombinant CP12 in a redox-independent manner. We have identified amino acid residues in the CP12 protein that are required for this new function preserving PRK activity. Numerous proteins involved in redox homeostasis and stress responses were more abundant and the expressions of various metabolic pathways were also increased or decreased in the absence of CP12. These results highlight CP12 as a moonlighting protein with additional functions beyond its well-known regulatory role in carbon metabolism.

The digestion of diacylglycerol isomers by gastric and pancreatic lipases and its impact on the metabolic pathways for TAG re-synthesis in enterocytes.

The specific activities of gastric and pancreatic lipases were measured using triacylglycerols (TAG) from rapeseed oil, purified 1,3-sn-DAG and 1,2(2,3)-sn-DAG produced from this oil, as well as a rapeseed oil enriched with 40% w/w DAG (DAGOIL). Gastric lipase was more active on 1,3-sn-DAG than on 1,2(2,3)-sn-DAG and TAG, whereas pancreatic lipase displayed a reverse selectivity with a higher activity on TAG than on DAG taken as initial substrates. However, in both cases, the highest activities were displayed on DAGOIL. These findings show that DAG mixed with TAG, such as in the course of digestion, is a better substrate for lipases than TAG. The same rapeseed oil acylglycerols were used to investigate intestinal fat absorption in rats with mesenteric lymph duct cannulation. The levels of TAG synthesized in the intestine and total fatty acid concentration in lymph were not different when the rats were fed identical amounts of rapeseed oil TAG, 1,2(2,3)-sn-DAG, 1,3-sn-DAG or DAGOIL. Since the lipolysis of 1,3-sn-DAG by digestive lipases leads to glycerol and not 2-sn-monoacylglycerol (2-sn-MAG) like TAG lipolysis, these results suggest that the re-synthesis of TAG in the enterocytes can entirely occur through the "glycerol-3-phosphate (G3P)" pathway, with the same efficiency as the 2-sn-MAG pathway predominantly involved in the intestinal fat absorption. These findings shed new light on the role played by DAG as intermediate lipolysis products. Depending on their structure, 1,2(2,3)-sn-DAG versus 1,3-sn-DAG, DAG may control the pathway (2-sn-MAG or G3P) by which TAG are re-synthesized in the enterocytes.

Cleaner degreasing of sheepskins by the Yarrowia lipolytica LIP2 lipase as a chemical-free alternative in the leather industry.

Conventional degreasing of skins and hides in the leather industry requires high amounts of organic solvents and detergents that cause environmental issues. In this study, the LIP2 lipase from the yeast Yarrowia lipolytica (YLLIP2) was shown to be effective in degreasing sheepskins, thus reducing the amount of harmful chemicals. Using 6 mg of lipase/kg of raw skin, successful degreasing was achieved in only 15 min at pH 8 and 30°C. ToF-SIMS mass spectra of chemically and enzymatically treated sheepskins are consistent with a selective elimination process for the enzymatic treatment. Comparative SEM microscopy, ATR-FTIR spectroscopy and physicochemical analyses showed better properties of the enzymatically treated leather than those of the chemical treatment. Effluent physicochemical parameters showed that the enzymatic treatment is a cleaner degreasing operation. Altogether, this work opens new horizons to use the YLLIP2 lipase as a more efficient alternative in the leather industry.

Fatty Acid Photodecarboxylase Is an Interfacial Enzyme That Binds to Lipid-Water Interfaces to Access Its Insoluble Substrate.

Fatty acid photodecarboxylase (FAP), one of the few natural photoenzymes characterized so far, is a promising biocatalyst for lipid-to-hydrocarbon conversion using light. However, the optimum supramolecular organization under which the fatty acid (FA) substrate should be presented to FAP has not been addressed. Using palmitic acid embedded in phospholipid liposomes, phospholipid-stabilized microemulsions, and mixed micelles, we show that FAP displays a preference for FAs present in liposomes and at the surface of microemulsions. The kinetics of adsorption onto phospholipid and galactolipid monomolecular films further suggests the ability of FAP to bind to and penetrate into membranes, with a higher affinity in the presence of FAs. The FAP structure reveals a potential interfacial recognition site with clusters of hydrophobic and basic residues surrounding the active site entrance. The resulting dipolar moment suggests the orientation of FAP at negatively charged interfaces. These findings provide important clues about the mode of action of FAP and the development of FAP-based bioconversion processes.

Quantitative monitoring of galactolipid hydrolysis by pancreatic lipase-related protein 2 using thin layer chromatography and thymol-sulfuric acid derivatization.

Galactolipids are the most abundant lipids on earth where they are mainly found in photosynthetic membranes of plant, algae, and cyanobacteria. Pancreatic lipase-related protein 2 (PLRP2) is an enzyme with galactolipase activity allowing mammals, especially herbivores, to digest this important source of fatty acids. We present a method for the quantitative analysis of galactolipids and galactosylated products resulting from their digestion by guinea pig PLRP2 (GPLRP2), using thin-layer-chromatography (TLC), thymol-sulfuric acid as derivatization reagent and scanning densitometry for detection. Thymol-sulfuric acid reagent has been used for the colorimetric detection of carbohydrates. It is shown here that the derivatization of galactosyl group from galactolipids by this reagent is not affected by the bound acyl glycerol, acyl chains length and number of galactose residues in the polar head. This allowed quantifying simultaneously the initial substrate and all galactosylated products generated upon the hydrolysis of monogalactosyl di-octanoylglycerol (C8-MGDG) by GPLRP2 using a single calibration with C8-MGDG as reference standard. The reaction products, monogalactosyl monooctanoyl glycerol (C8-MGMG) and monogalactosyl glycerol (MGG), were identified and quantified, MGG being recovered from the aqueous phase and analyzed by a separate TLC analysis. This method is therefore suitable to quantify the products resulting from the release of both fatty acids present in MGDG and thereby shows that PLRP2 can contribute to the complete digestion of galactolipids and further intestinal absorption of their fatty acids.

Evaluation of vitamin D bioaccessibility and mineral solubility from test meals containing meat and/or cereals and/or pulses using in vitro digestion.

In this study, we evaluated vitamin D and mineral (iron, zinc, magnesium) transfer to the bolus aqueous phase during the digestion of meals with/without pulses. We performed in vitro digestions using test meals made either of i) beef and/or semolina and/or chickpeas, or of ii) potatoes supplemented or not with fibers, phytates, tannins and saponins. Chickpea presence led to a decrease in vitamin D bioaccessibility (-56%, p ≤ 0.05) and mineral solubility (-28% for iron, p ≤ 0.05) compared with meals with beef and/or semolina only. This effect was largely compensated for vitamin D by the fact that this vitamin was more stable during digestion of meals based on plant foods only than of meals with beef. Tannins were the most deleterious compounds for iron solubility, while phytates and tannins decreased vitamin D bioaccessibility. Agronomical or technical solutions to selectively decrease the amount in pulses of compounds that affect micronutrient bioavailability should be further explored.

The 1,2-o-dilauryl-rac-glycero-3-glutaric acid-(6'-methylresorufin) ester (DGGR) lipase assay in cats and dogs is not specific for pancreatic lipase.

BACKGROUND: The measurement of pancreatic lipase is important for the diagnosis of feline and canine pancreatitis. Recent studies have claimed that lipase assays using the 1,2-o-dilauryl-rac-glycero-3-glutaric acid-(6'-methylresorufin) ester (DGGR) as a substrate are more specific for measuring pancreatic lipase than traditional lipase assays. However, the analytical specificity of this assay for pancreatic lipase has not been demonstrated. OBJECTIVES: We aimed to determine whether hepatic and/or lipoprotein lipases can interfere with the DGGR-based assay results in cats and dogs. We, therefore, compared plasma lipase activities measured using DGGR-based and pancreatic lipase immunoreactivity (PLI) assays before and after administering heparin, known to cause the release of hepatic and lipoprotein lipases, in cats and dogs. METHODS: Heparin was administered in six cats and six dogs. Blood was collected at baseline and 10, 20, 30, 60, and 120 minutes after heparin administration. Lipase activity was measured using a DGGR-based assay, and PLI concentrations were measured using the Spec fPL and cPL assays for cats and dogs, respectively. RESULTS: Plasma lipase activities, as measured using the DGGR-based assay, increased significantly 10 minutes after heparin administration in both cats (P = .003) and dogs (P = .006) and returned to baseline by 120 minutes. In contrast, PLI concentrations showed no significant changes after heparin administration. CONCLUSIONS: DGGR is not only hydrolyzed by pancreatic lipase but also by hepatic lipase, lipoprotein lipase, or both, in cats and dogs. Since these extrapancreatic lipases are also naturally present in cats and dogs, they could contribute to the lack of analytical specificity for the DGGR-based assays.

Oleochemistry potential from Brazil northeastern exotic plants.

Caatinga is a Brazilian semi-arid ecosystem that stands out for presenting unique environmental characteristics with a dry, spiny and deciduous shrub/forest vegetation with several species that can be renewable oil sources with potential applicability in oleochemical and nutrition. Caatinga oilseeds have a high content of unsaturated fatty acids, phytosterols and sterols, and this composition is related to its nutritional potential. The present review summarizes the knowledge on the oil contents and fatty acid profiles of seeds from six representatives caatinga species. It was observed that plants species like Caju (Anacardium occidentale L.), Favela (Cnidoscolus quercifolius Pohl), Licuri (Syagrus coronata (Mart.) Becc.), Pinhão-bravo (Jatropha mollissima Pohl Baill), Pequi (Caryocar brasiliense Camb) and Oiticica (Licania rígida Benth) contains approximately 33.1, 33.5, 49.2, 18.3, 70.16 and 57.0% w/w of oil, respectively, on a dry weight basis. Their fatty acid profiles are mostly saturated for Licuri oil, with a high content of lauric acid (up to 40%) and unsaturated for Favela, Pinhão-bravo, Cashew nut, Pequi and Oiticica oils. Oiticica oil shows a high concentration of unusual conjugated polyunsaturated fatty acids, like α-Eleostearic and Licanic acid with 16.90 and 43.20% w/w, respectively.

The digestion of galactolipids and its ubiquitous function in Nature for the uptake of the essential α-linolenic acid.

Galactolipids, mainly monogalactosyl diglycerides and digalactosyl diglycerides are the main lipids found in the membranes of plants, algae and photosynthetic microorganisms like microalgae and cyanobacteria. As such, they are the main lipids present at the surface of earth. They may represent up to 80% of the fatty acid stocks, including a large proportion of polyunsaturated fatty acids mainly α-linolenic acid (ALA). Nevertheless, the interest in these lipids for nutrition and other applications remains overlooked, probably because they are dispersed in the biomass and are not as easy to extract as vegetable oils from oleaginous fruit and oil seeds. Another reason is that galactolipids only represent a small fraction of the acylglycerolipids present in modern human diet. In herbivores such as horses, fish and folivorous insects, galactolipids may however represent the main source of dietary fatty acids due to their dietary habits and digestion physiology. The development of galactolipase assays has led to the identification and characterization of the enzymes involved in the digestion of galactolipids in the gastrointestinal tract, as well as by microorganisms. Pancreatic lipase-related protein 2 (PLRP2) has been identified as an important factor of galactolipid digestion in humans, together with pancreatic carboxyl ester hydrolase (CEH). The levels of PLRP2 are particularly high in monogastric herbivores thus highlighting the peculiar role of PLRP2 in the digestion of plant lipids. Similarly, pancreatic lipase homologs are found to be expressed in the midgut of folivorous insects, in which a high galactolipase activity can be measured. In fish, however, CEH is the main galactolipase involved. This review discusses the origins and fatty acid composition of galactolipids and the physiological contribution of galactolipid digestion in various species. This overlooked aspect of lipid digestion ensures not only the intake of ALA from its main natural source, but also the main lipid source of energy for growth of some herbivorous species.