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1.
MurNAc etherases cleave the uniqued-lactyl ether bond of the bacterial cell wall sugar N-acetylmuramic acid (MurNAc). Members of this newly discovered family of enzymes are widely distributed among bacteria and
are required to utilize peptidoglycan fragments obtained either from the environment or from the endogenous cell wall (i.e.,
recycling). MurNAc etherases are strictly dependent on the substrate MurNAc possessing a free reducing end and a phosphoryl
group at C6. They carry a single conserved sugar phosphate isomerase/sugar phosphate- binding (SIS) domain to which MurNAc
6-phosphate is bound. Two subunits form an enzymatically active homodimer that structurally resembles the isomerase module
of the double-SIS domain protein GlmS, the glucosamine 6-phosphate synthase. Structural comparison provides insights into
the two-step lyase-type reaction mechanism of MurNAc etherases: β-elimination of the D-lactic acid substituent proceeds through
a 2,3-unsaturated sugar intermediate to which water is subsequently added.
Received 31 August 2007; received after revision 12 October 2007; accepted 1 November 2007 相似文献
2.
P. E. Pilet 《Cellular and molecular life sciences : CMLS》1998,54(8):851-865
Several characteristics of the plant hormone abscisic acid (ABA) are critically discussed, more or less directly, in relation to the extension of root cells. A few topics have been selected some biochemical characteristics of ABA (chemical structure, metabolism), inhibiting-β complex, inhibiting regulators from root caps, endogenous ABA in growing roots (ABA gradients, microsurgical experiments, light effects), applied ABA on elongating roots, ABA and indol-3yl acetic acid (IAA) interactions (root growth, proton extrusion, hormone transport, auxin herbicides), ABA effect on the root cell cycle, ABA and drought cells of elongating roots [water deficit conditions, IAA and jasmonic acid (JA) as ‘stress hormones’ other than ABA, gene expression]. Received 28 January 1998; received after revision 20 April 1998; accepted 21 April 1998 相似文献
3.
AMP-activated protein kinase in skeletal muscle: From structure and localization to its role as a master regulator of cellular metabolism 总被引:1,自引:0,他引:1
Witczak CA Sharoff CG Goodyear LJ 《Cellular and molecular life sciences : CMLS》2008,65(23):3737-3755
The AMP-activated protein kinase (AMPK) is a metabolite sensing serine/threonine kinase that has been termed the master regulator
of cellular energy metabolism due to its numerous roles in the regulation of glucose, lipid, and protein metabolism. In this
review, we first summarize the current literature on a number of important aspects of AMPK in skeletal muscle. These include
the following: (1) the structural components of the three AMPK subunits (i.e. AMPKα, β, and γ), and their differential localization
in response to stimulation in muscle; (2) the biochemical regulation of AMPK by AMP, protein phosphatases, and its three known
upstream kinases, LKB1, Ca2+/calmodulin-dependent protein kinase kinase (CaMKK), and transforming growth factor-β-activated kinase 1 (TAK1); (3) the pharmacological
agents that are currently available for the activation and inhibition of AMPK; (4) the physiological stimuli that activate
AMPK in muscle; and (5) the metabolic processes that AMPK regulates in skeletal muscle.
Received 04 May 2008; received after revision 14 June 2008; accepted 14 July 2008 相似文献