BACKGROUND Penicillin G acylase of Escherichia coli (PGAEc) is a commercially valuable enzyme for which efficient bacterial expression systems have been developed. The enzyme is used as a catalyst for the hydrolytic production of beta-lactam nuclei or for the synthesis of semi-synthetic penicillins such as ampicillin, amoxicillin and cephalexin. To become a mature, periplasmic enzyme, the inact...

Acylases catalyze the hydrolysis of a range of S-substituted N-acetyl-L-cysteines. The hydrolysis of N-acetyl-L-cysteine is catalyzed by cytosolic acylase I, and activity is present in human endothelial cells and rat lung, intestinal, and liver homogenates. Many haloalkenes are metabolized to mercapturates, which also undergo acylase-catalyzed hydrolysis. The acylases that catalyze the deacetyl...

The pga gene of Escherichia coli W ATCC11105 encodes a penicillin G acylase whose expression is regulated at both the transcriptional and post-transcriptional level. In this work we have shown that PaaX is the repressor of pga expression, and we have identified its binding consensus as TGATTC(N27)GAATCA. We conclude that the process of "PAA induction" actually involves relief of pga from repres...

We study the canonical stability of a smooth projective 3-fold V of general type. We prove that |5KV | gives a birational map onto its image provided pg ≥ 4. For those V with pg = 3, |6KV | gives a birational map. Known examples show that both the results are optimal.

An (n, r)-arc is a set of n points of a projective plane such that some r, but no r + 1 of them, are collinear. In this paper new (95, 7)-arc, (183, 12)-arc, (205, 13)-arc in PG(2,17) and (243, 14)-arc, (264, 15)-arc in PG(2,19) are constructed.