Characteristics of a low affinity passive Ca2+ influx component in rat parotid gland basolateral plasma membrane vesicles.

We have previously reported the presence of two Ca2+ influx components with relatively high (KCa = 152 +/- 79 microM) and low (KCa = 2.4 +/- 0.9 mM) affinities for Ca2+ in internal Ca2+ pool-depleted rat parotid acinar cells [Chauthaiwale et al.

Presence of two Ca2+ influx components in internal Ca2+-pool-depleted rat parotid acinar cells.

The molecular mechanism(s) involved in mediating Ca2+ entry into rat parotid acinar and other non-excitable cells is not known. In this study we have examined the kinetics of Ca2+ entry in fura-2-loaded parotid acinar cells, which were treated with thapsigargin to deplete internal Ca2+ pools (Ca2+-pool-depleted cells). The rate of Ca2+ entry was determined by measuring the initial increase in free cytosolic [Ca2+] ([Ca2+]i) in Ca2+-pool-depleted, and control (untreated), cells upon addition of various [Ca2+] to the medium.

Reconstitution of a passive Ca(2+)-transport pathway from the basolateral plasma membrane of rat parotid gland acinar cells.

We have previously reported that rat parotid gland basolateral plasma membrane vesicles (BLMV) have a relatively high affinity Ca2+ transport pathway and an unsaturable Ca2+ flux component (Lockwich et al., 1994. J.

Production and Purification of Extracellular D-Xylose Isomerase from an Alkaliphilic, Thermophilic Bacillus sp.

An alkaliphilic, thermophilic Bacillus sp. (NCIM 59) produced extracellular xylose isomerase at pH 10 and 50 degrees C by using xylose or wheat bran as the carbon source. The distribution of xylose isomerase as a function of growth in comparison with distributions of extra- and intracellular marker enzymes such as xylanase and beta-galactosidase revealed that xylose isomerase was truly secreted as an extracellular enzyme and was not released because of sporulation or lysis.

Chemical modification of xylanase from alkalothermophilic Bacillus species: evidence for essential carboxyl group.

The role of carboxyl group in the catalytic action of xylanase (M(r) 35,000) from an alkalothermophilic Bacillus sp. was delineated through kinetic and chemical modification studies using Woodward's Reagent K. The kinetics of inactivation indicated that one carboxyl residue was essential for the xylanase activity with a second order rate constant of 3300 M-1 min-1.

Specific interaction of guanidine hydrochloride with essential carboxyl group of xylanase from alkalothermophilic Bacillus sp.

Experimental evidence for the specific interaction of guanidine hydrochloride with the carboxyl group of xylanase has been presented for the first time. Guanidine hydrochloride (0.1 M) inactivated the xylanase from alkalothermophilic Bacillus sp.