Sequence homology, enzyme

In Bacillus snbtilis these two reactions are catalyzed by two separate enzymes that have amino acid sequences homologous to the corresponding regions of the bifunctional enzyme from E. coli, and thus each forms a barrel... 

Crystallographic studies imply that although little sequence homology exists between the different protease cleavage sites, what is conserved is the shape that they adopt within the active site of the enzyme (Prabu-Jeyabalan et al. 2002). This shape has been termed the substrate envelope and represents the consensus volume overlapping the majority of the substrates. Most likely, HIV-1 protease recognizes a particular peptide sequence as being a substrate by a combination of accessibility and the shape the sequence can adopt. 

The DBT sulfone monooxygenase (TdsA) from Paenibacillus sp. strain All-2 has been isolated and characterized by Konishi et al [162], This enzyme was compared with the mesophilic enzyme dszA from R. erythropolis and found to have very little sequence homology however, had similar properties. The molecular mass of the enzyme TdsA was calculated by gel filtration and found to be 120 KDa, whereas with a subunit molecular mass calculated by SDS-PAGE to be 48 KDa. 

In general, the 10 different forms of adenylyl cyclase can be divided into three major and two minor groups based on their functional attributes as well as on their sequence homology. The three major families are (1) the Ca2+/calmodulin-stimulated isoforms, which include AC1, AC3, and AC8 certain of these enzymes are inhibited by GPt (2) the G[ -stimulated isoforms, which include AC2, AC4, and AC7 and (3) the Ca2+ and Gai inhibited isoforms, which are AC5 and AC6. The other two categories each have a single member (4) AC9, which is the most divergent of the membrane-bound isoforms, is stimulated by G(IS, inhibited by calcineurin (a protein phosphatase), and is insensitive to forskolin (5) sAC, the only soluble isoform, is the most divergent and is most similar to the adenylyl cyclase found in Cyanobacteria. 

The standard model for the preclinical development of anti-osteoporosis therapies is the ovariectomized (OVX) rat. However, Cat K inhibitors developed specifically against the human enzyme are generally significantly less potent ( 2-orders of magnitude) against the rat and mouse enzymes than against human Cat K [9]. This loss of potency towards the rodent enzymes, which is consistent with their low sequence homology, therefore restricts the use of... 

A third member of this family, an extracellular oxidase, has also been identified by sequence homology (118). This homology may indicate that the (tyrosyl)Cu(II) motif is not unique for one enzyme but may represent a common structural motif for a class of enzymes. 

The biogenic amines are the preferred substrates of MAO. The enzyme comes in two flavors, MAO-A and MAO-B, both of which, like FMO, rely on the redox properties of FAD for their oxidative machinery. The two isoforms share a sequence homology of approximately 70% (81) and are found in the outer mitochondrial membrane, but they differ in substrate selectivity and tissue distribution. In mammalian tissues MAO-A is located primarily in the placenta, gut, and liver, while MAO-B is predominant in the brain, liver, and platelets. MAO-A is selective for serotonin and norepinephrine and is selectively inhibited by the mechanism-based inhibitor clorgyline (82). MAO-B is selective for /1-phcncthylaminc and tryptamine, and it is selectively inhibited by the mechanism-based inhibitors, deprenyl and pargyline (82) (Fig. 4.32). Recently, both MAO-A (83) and MAO-B (84) were structurally characterized by x-ray crystallography. 

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