Lipase consensus sequence

GXSXG lipase consensus sequence Ca2+-independent catalytic activity... 

GXSXG lipase consensus sequence 8 an-kyrin repeats Ca2+-in-dependent catalytic activity, proline-rich consensus motif (PX5PX8HHPX12NX4Q), LH-iPLA 2 (long isoform, 88 kDa) but not SH-iPLA2 (short isoform, 85 kDa) is activated by ATP GDSXV modified consensus sequence of serine esterase family catalytic triad Ser-His-Asp P and y subunits form a heter-otrimer with a 45-kDa noncatalytic subunit Ca2+-indepen-dent catalytic activity 0 Ca2+-independent catalytic activity... 

Ser-228 in GXSXG lipase consensus sequence, CaLB domain, responsive to PIP2 for catalytic activity and membrane association, multiple serine phosphorylation sites... 

Two types of PLAjS, type I and type II, have been described, with different amino acid sequences (Tab. 2.1). Most PLAiS of both types contain a lipase consensus sequence (GXSXG). An exception is PA-PLAi (type II), which contains SXSXG. 

Lipase Aspergillus niger)-mediated saponification of heptyl esters is employed for the C-terminal deprotection of several phosphopeptides. For example this method has been used in the synthesis (Scheme 24) of a consensus sequence of the Raf- kinase. 

Until recently relatively little was known about the molecular basis of lipid hydrolysis. The first amino acid sequence of a triacylglycerol lipase was given by De Caro et al. (1981). As more sequence data became available, it was noted that lipases and esterases share a short consensus sequence, G-X-S-X-G (Boel et al., 1988 Datta et al., 1988 Antonian, 1988 Brenner, 1988). The role of the invariant serine at the center of this sequence was debated (Maraganore and Heinrikson, 1986). Some authors speculated about a lipid recognition site, others compared this pentapeptide to the sequence around the nucleophilic serine in serine proteinases. 

The catalytic site in RmL was identified originally from the location of the known lipase/esterase consensus sequence G-X-S-X-G (Brenner, 1988) containing the nucleophilic serine (Ser-144). This amino acid was found to be involved in a hydrogen-bonded constellation also including His-257 and Asp-203. Overall this hydrogen-bonding network is very reminiscent of the catalytic triad of serine proteinases. However, in contrast to proteinases, the triad is concealed under a short helix, the lid, and is therefore inaccessible to solvent. 

The next interesting question is whether the consensus sequence shared by lipases and esterases corresponds to a common conserved structural motif. In all three known structures of lipases (RmL, hPL,... 

The cDNA-derived amino acid sequences of human gastric lipase (Bodmer et ai, 1987) and rat lingual lipase (Docherty et al., 1985) show clear homology, with 78% identity. There are 379 and 377 amino acids, respectively, and three of the four putative glycosylation sites in the human enzyme were also found in the rat lingual protein. However, with the exception of the G-X-S-X-G consensus sequence motif, there appears to be no homology with any other lipase family. 

The crystal structure of the HGL, expressed in baculovirus/insect ci ll system was obtained at 3 A resolution [35]. This structure was the first to be resolved within the acidic lipases family. HGL is a globular protein that exhibits the a/ hydrolase fold (Fig. 9.2). The final model contains residues 9 to 53 and 57 to 379, six sugar residues located on the four potential N-glycosylation sites and a disulfide bridge Cys 227-Cys 236, whereas Cys 244 is free (Fig. 9.2). In hpases, as weU as in serine proteases [36], the catalytic machinery consists of a triad and an oxyariiori hole. In HGL, the nucleophilic serine (Ser 153) belonging to the usual consensus sequence G-X-S-X-G is located at the cormection between an a hehx and a f strand has an e conformation, which are characteristic features of all enzymes within the alP hydrolase fold family ]21]. His 353 and Asp 324 are the other two residues... 

Finally we tested the two immunsera by western blot on a pure hog pancreatic lipase. Only the lower immunserum was reactive with this lipase. The cross reactivity with an animal lipase involves primary sequence epitopes rather than conformational epitopes. These two molecules have a sequence homology. Probably the consensus sequence Gly - X - Ser - X - Gly commonly present in animal and microbial lipases (Antonian, 1988 Blow, 1990 ). 

The earliest observation that implied evolutionary links between all lipases was that of the consensus pentapeptide G-X-S-X-G, subsequently shown to contain the nucleophilic serine. The apparent similarity of this sequence to that found around the active serine in the chy-motrypsin and subtilisin families of serine proteinases prompted a number of authors to infer an evolutionary relationship between the three families. Further evidence in support of such a link came from secondary structure prediction studies indicating that the nucleophilic serine in a lipase is most likely within a /3 turn, structurally reminiscent of proteinases (Reddy et ai, 1986). In fact, one of the commonly used phrases found in introductions to many papers dealing directly or indirectly with lipases refers to the consensus G-X-S-X-G pentapeptide found in the active site of all serine proteinases and esterases. We now know that the implication that homology and/or structural similarities exist between the enzymes belonging to these diverse groups is incorrect. The matter has been dealt with in the literature (Derewenda and Derewenda, 1991 Liao et ai, 1992), but it seems appropriate to review some of the conclusions. 

The close proximity of the jS strand and of the helix enforced by the sharpness of the turn containing the G-X-S-X-G pentapeptide leads to a number of close contacts between amino acids from these two secondary structure elements (Fig. 12). It was this repetitive pattern of small and/or hydrophobic residues observed in amino acid sequences adjacent to the consensus pentapeptide that originally prompted De-rewenda and Derewenda (1991) to postulate that, in all lipases/esterases in which the G-X-S-X-G motif contains the nucleophile, the structure of this pentapeptide will be similar to that of RmL. So far all experimental data support this conclusion (see Section IV,B and Table V). 

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